RFR: 8308116: jdk.test.lib.compiler.InMemoryJavaCompiler.compile does not close files

[Axel Boldt-Christmas]

jdk.test.lib.compiler.InMemoryJavaCompiler.compile(String className, CharSequence sourceCode, String... options) creates a JavaFileManager but fails to close it after the CompilationTask is completed, leaving the file descriptors open until reference processing kicks in.

Graph below shows number of open file descriptors before and after this patch for a program which compiles dummy classes in a loop. 
<img width="1116" alt="Before and after" src="https://github.com/openjdk/jdk/assets/1139284/1ecfb32a-735b-4765-bcca-81f67a4c9816">

Testing: GHA and Oracle CI tier1-3. Tests using jdk.test.lib.compiler.InMemoryJavaCompiler also tested locally.

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Commit messages:
 - Fix tests
 - 8308116: jdk.test.lib.compiler.InMemoryJavaCompiler.compile does not close files

Changes: https://git.openjdk.org/jdk/pull/14001/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14001&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8308116
  Stats: 57 lines in 6 files changed: 45 ins; 2 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/14001.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14001/head:pull/14001

PR: https://git.openjdk.org/jdk/pull/14001