RFR: 8308116: jdk.test.lib.compiler.InMemoryJavaCompiler.compile does not close files [v3]

[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.

Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision:

  Apply suggestions from code review
  
  Co-authored-by: Andrey Turbanov <turbanoff at gmail.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/14001/files
  - new: https://git.openjdk.org/jdk/pull/14001/files/a939e0c9..99fde73c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14001&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14001&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 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