Introduce top-down action caching in Bazel. The top-down cache may be provided by a Bazel module.

The cache works by first computing a _transitive_ cache key for the action, known as a sketch. It composes the action keys for all dependent actions and all transitive source file digest hashes.

This feature is not currently wired up for use - consider it extremely experimental at this point.

RELNOTES: None
PiperOrigin-RevId: 260973078

src/test/java/com/google/devtools/build/lib/skyframe/BUILD

diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/BUILD b/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
index 968c424..71cba10 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
@@ -78,6 +78,7 @@
         "//src/main/java/com/google/devtools/build/lib:util",
         "//src/main/java/com/google/devtools/build/lib/actions",
         "//src/main/java/com/google/devtools/build/lib/actions:localhost_capacity",
+        "//src/main/java/com/google/devtools/build/lib/actionsketch:action_sketch",
         "//src/main/java/com/google/devtools/build/lib/analysis/platform",
         "//src/main/java/com/google/devtools/build/lib/causes",
         "//src/main/java/com/google/devtools/build/lib/clock",