RFR: JDK-8327474 Review use of java.io.tmpdir in jdk tests [v3]

[Bill Huang]

> This task addresses an essential aspect of our testing infrastructure: the proper handling and cleanup of temporary files and socket files created during test execution. The motivation behind these changes is to prevent the accumulation of unnecessary files in the default temporary directory, which can affect the system's storage and potentially influence subsequent test runs.
> 
> Our review identified that several tests create temporary files or socket files without ensuring their removal post-execution. 
> - Direct calls to java.io.File.createTempFile and java.nio.file.Files.createTempFile without adequate cleanup.
> - Tests using NIO socket channels with StandardProtocolFamily.UNIX, not explicitly removing socket files post-use.

Bill Huang has updated the pull request incrementally with one additional commit since the last revision:

  Fixed potential NPE issues.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18352/files
  - new: https://git.openjdk.org/jdk/pull/18352/files/620f9259..2517f756

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18352&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18352&range=01-02

  Stats: 11 lines in 4 files changed: 5 ins; 1 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/18352.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18352/head:pull/18352

PR: https://git.openjdk.org/jdk/pull/18352