RFR: 8321288: [JVMCI] HotSpotJVMCIRuntime doesn't clean up WeakReferences in resolvedJavaTypes

[Tom Rodriguez]

HotSpotJVMCIRuntime.resolvedJavaTypes implements a weak value map but is lacking code to clean out cleared weak references.  In normal mixed execution this isn't likely to get big and generally isolates are shutdown frequently so this doesn't lead to problems.  In Xcomp mode with tests that stress unloading this becomes more problematic.  In the worst case is still doesn't lead to large heaps but does make the idle heap larger than required.

This PR adds ReferenceQueue based cleaning of reclaimed values.  Testing in the context of a long running isolate shows that they are no longer accumulating.

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Commit messages:
 - 8321288: [JVMCI] HotSpotJVMCIRuntime doesn't clean up WeakReferences in resolvedJavaTypes

Changes: https://git.openjdk.org/jdk/pull/16981/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16981&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321288
  Stats: 34 lines in 1 file changed: 31 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16981.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16981/head:pull/16981

PR: https://git.openjdk.org/jdk/pull/16981