[copybara-service]

Fix and update Bazel build/test configuration:

• Run Bazel CI tests under the configured matrix JDK runtimes rather than always using .bazelrc's default runtime (which prior to this CL was JDK 21).
• Standardize the version matrix on [8, 11, 25].
  • I will have to bypass the Copybara presubmit for this CL because it will still be looking for a JDK 22 Flogger job instead of the new JDK 25 job (b/360096677). Maybe I should rename all our projects' "25" jobs to "latest LTS"....
  • I will "have to" update the Flogger branch-protection rules to require the new JDK 25 job instead of the JDK 22 job that I'm removing. (IIRC, nothing actually blocks on that, but it's nice for it to match our "real" rules.)
    • Huh, apparently GitHub is nudging me from branch-protection rules to "rulesets." I'm not going to worry about that now.
• For Bazel toolchain/exec operations, use a JDK 25 (including allowing Java 25 language features), and for the bazel/mvn VM itself, have CI request JDK 27.
  • 25 (as the most recent LTS) is the newest version that Bazel has available for automatic download across all platforms. (It has 27 for Linux only.)
• For selecting the language version, use --java_language_version=8 instead of --release or -source -target. It's shorter and more standard, and Bazel even silences the deprecation warning that we'd otherwise see when targeting 8.
• Remove redundant debug-info javac options (-g) in Flogger: rules_java enables it (along with -parameters) by default nowadays.
• Enable --experimental_one_version_enforcement=error as widely as we can.
• Upgrade Flogger's bazel_common dep.
• Set test --test_env=TZ=UTC.
• Configure ci.yml to cache the right(?) Bazel information (~/.cache/bazel/*/cache, including cache/repos/v1, instead of ~/.cache/bazel/*/*/external).

Prep work:

• Skip Flogger tests that use Mockito under Java 8. Mockito 5+ requires Java 11+. (It would make sense to skip under Java 9 and Java 10, too, but meh.)
• Set --jvmopt=-Dnet.bytebuddy.experimental=true for Flogger to enable support for Java-25 class files.

Compare cl/996591293.

RELNOTES=n/a