All BazelCI platforms use explicit digests (#2763)

buildkite/bazelci.py

diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index 504dafd..fb7d7cf 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -280,6 +280,19 @@
     "debian11-java17": "sha256:54d454bb70f6adf820bdd848f2a0cdf7cf484e4e1f50550507189e2faae6604b",
     "debian12": "sha256:eb08f90b82484accacfd3724b987cb814b28b871588df19bdb910625f70ff980",
     "debian13": "sha256:e77f3daacbd48bddcd695b1edde610f488d8f8c06c404b4f6d0039a817c673b6",
+    "ubuntu1604-java8": "sha256:9e5e7c5383c4a8e919d02fd81d7197bd76e912b465511dab7b45336ca3b193d0",
+    "ubuntu1804-java11": "sha256:613a16d8f8de3fa846d3ae563cbc9e8a7950765f6f484e9ed29deb26218eb594",
+    "ubuntu2004-java11": "sha256:8719817e16ed70b61e8cc004ad884ddf7e0db2f994182eafbb4819bc6a52ff20",
+    "ubuntu2004": "sha256:501a6302b6f518c68ec12afd1f4e30fe4b48c46eea3b1f3fbcc35f922e0f2802",
+    "ubuntu2204": "sha256:7ff0dc93cbb73e159747149b7e51f6d9ea0133bff1e72aa05588d84241f68370",
+    "ubuntu2404": "sha256:73f654103b960bb0fffe63f2a01b07e76f04c31e2e0ae0d9b45500f09f458d27",
+    "ubuntu2004-kythe": "sha256:3862183a7674064e7e36ab851166e5a20eaccb47c8dd7205354fc8de6a6be0e9",
+    "ubuntu2204-kythe": "sha256:4efd27dc071a031fd0550cd59931f4a26d4531c80356e540ab9e9969b4bf1bbc",
+    "ubuntu2404-kythe": "sha256:2958a2329d7bbb01edde128a0036829f0c64074ffd1e304a2b4692666a5e0f66",
+    "ubuntu2204-java17": "sha256:3f5eeb409d9c2f3da4e162b6e64527a158a02443d2bb77a41890ddcdf7a7293a",
+    "fedora39-java17": "sha256:2886ccd5adb6b8941bfe18cbba1acbb34c833fac635aab3b80493bfc5ba2dbcd",
+    "fedora40-java21": "sha256:857e3d7cda608fd2fd9a2d1455b9b09db6979aff4250061e61b9929a10690e90",
+    "fedora43-java25": "sha256:30cf2aa0a491a208efde941b42504785f957f0c2f904aa5ef7f33438c822713b",
 }
 
 
@@ -379,35 +392,35 @@
         "name": "Ubuntu 16.04 LTS (OpenJDK 8, gcc 5.4.0)",
         "emoji-name": ":ubuntu: Ubuntu 16.04 LTS (OpenJDK 8, gcc 5.4.0)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu1604-java8",
+        "docker-image": get_docker_image("ubuntu1604-java8"),
         "python": "python3",
     },
     "ubuntu1804": {
         "name": "Ubuntu 18.04 LTS (OpenJDK 11, gcc 7.5.0)",
         "emoji-name": ":ubuntu: Ubuntu 18.04 LTS (OpenJDK 11, gcc 7.5.0)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu1804-java11",
+        "docker-image": get_docker_image("ubuntu1804-java11"),
         "python": "python3",
     },
     "ubuntu2004_java11": {
         "name": "Ubuntu 20.04 LTS (OpenJDK 11, gcc 9.4.0)",
         "emoji-name": ":ubuntu: Ubuntu 20.04 LTS (OpenJDK 11, gcc 9.4.0)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2004-java11",
+        "docker-image": get_docker_image("ubuntu2004-java11"),
         "python": "python3.8",
     },
     "ubuntu2004": {
         "name": "Ubuntu 20.04 LTS",
         "emoji-name": ":ubuntu: Ubuntu 20.04 LTS",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2004",
+        "docker-image": get_docker_image("ubuntu2004"),
         "python": "python3.8",
     },
     "ubuntu2004_arm64": {
         "name": "Ubuntu 20.04 LTS ARM64",
         "emoji-name": ":ubuntu: Ubuntu 20.04 LTS ARM64",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2004",
+        "docker-image": get_docker_image("ubuntu2004"),
         "python": "python3.8",
         "queue": "arm64",
     },
@@ -415,7 +428,7 @@
         "name": "Ubuntu 22.04 LTS ARM64",
         "emoji-name": ":ubuntu: Ubuntu 22.04 LTS ARM64",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2204",
+        "docker-image": get_docker_image("ubuntu2204"),
         "python": "python3",
         "queue": "arm64",
     },
@@ -423,7 +436,7 @@
         "name": "Ubuntu 24.04 LTS ARM64",
         "emoji-name": ":ubuntu: Ubuntu 24.04 LTS ARM64",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2404",
+        "docker-image": get_docker_image("ubuntu2404"),
         "python": "python3",
         "queue": "arm64",
     },
@@ -431,63 +444,63 @@
         "name": "Kythe (Ubuntu 20.04 LTS)",
         "emoji-name": "Kythe (:ubuntu: Ubuntu 20.04 LTS)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2004-kythe",
+        "docker-image": get_docker_image("ubuntu2004-kythe"),
         "python": "python3.8",
     },
     "kythe_ubuntu2204": {
         "name": "Kythe (Ubuntu 22.04 LTS)",
         "emoji-name": "Kythe (:ubuntu: Ubuntu 22.04 LTS)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2204-kythe",
+        "docker-image": get_docker_image("ubuntu2204-kythe"),
         "python": "python3",
     },
     "kythe_ubuntu2404": {
         "name": "Kythe (Ubuntu 24.04 LTS)",
         "emoji-name": "Kythe (:ubuntu: Ubuntu 24.04 LTS)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2404-kythe",
+        "docker-image": get_docker_image("ubuntu2404-kythe"),
         "python": "python3",
     },
     "ubuntu2204_java17": {
         "name": "Ubuntu 22.04 (OpenJDK 17, gcc 11.2.0)",
         "emoji-name": ":ubuntu: Ubuntu 22.04 (OpenJDK 17, gcc 11.2.0)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2204-java17",
+        "docker-image": get_docker_image("ubuntu2204-java17"),
         "python": "python3",
     },
     "ubuntu2204": {
         "name": "Ubuntu 22.04",
         "emoji-name": ":ubuntu: Ubuntu 22.04 LTS",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2204",
+        "docker-image": get_docker_image("ubuntu2204"),
         "python": "python3",
     },
     "ubuntu2404": {
         "name": "Ubuntu 24.04",
         "emoji-name": ":ubuntu: Ubuntu 24.04 LTS",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/ubuntu2404",
+        "docker-image": get_docker_image("ubuntu2404"),
         "python": "python3",
     },
     "fedora39": {
         "name": "Fedora 39 (OpenJDK 17, gcc 13.1.1)",
         "emoji-name": ":fedora: Fedora 39 (OpenJDK 17, gcc 13.1.1)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/fedora39-java17",
+        "docker-image": get_docker_image("fedora39-java17"),
         "python": "python3",
     },
     "fedora40": {
         "name": "Fedora 40 (OpenJDK 21, gcc 14.1.1)",
         "emoji-name": ":fedora: Fedora 40 (OpenJDK 21, gcc 14.1.1)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/fedora40-java21",
+        "docker-image": get_docker_image("fedora40-java21"),
         "python": "python3",
     },
     "fedora43": {
         "name": "Fedora 43 (OpenJDK 25, gcc 15.2.1)",
         "emoji-name": ":fedora: Fedora 43 (OpenJDK 25, gcc 15.2.1)",
         "publish_binary": [],
-        "docker-image": f"gcr.io/{DOCKER_REGISTRY_PREFIX}/fedora43-java25",
+        "docker-image": get_docker_image("fedora43-java25"),
         "python": "python3",
     },
     "macos": {