Delete code associated with `--experimental_dynamic_configs=retroactive`.

This flag value is unused and untested outside of a couple unit tests for individual components. Removing it simplifies work on b/185778053, specifically unblocking the removal of `BuildOptions.DiffForReconstruction`.

Also took this opportunity to apply fixes to warnings in the affected files.

PiperOrigin-RevId: 369970226

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 fef712a..7739ef0 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/BUILD
@@ -8,7 +8,7 @@
 filegroup(
     name = "srcs",
     testonly = 0,
-    srcs = glob(["**"]) + ["//src/test/java/com/google/devtools/build/lib/skyframe/trimming:srcs"],
+    srcs = glob(["**"]),
     visibility = ["//src/test/java/com/google/devtools/build/lib:__pkg__"],
 )