RFR: 8366582: Test jdk/jshell/ToolSimpleTest.java failed: provider not found

[Jan Lahoda]

The `jdk/jshell/ToolSimpleTest.java` randomly fails, the reason is this: when indexing the bootclasspath/`PLATFORM_CLASS_PATH`, `$JDK_HOME/lib/modules` is typically there, but it can't be opened as a FileSystem, and the exception is sent to the debugging facility. The debugging facility typically does nothing, but in this test contains a test case that enabled debugging, and if the order of things is that the debugging is first enabled, and then the `ProviderNotFoundException` is reported, the test fails.

The proposal herein is to not to try to open `$JDK_HOME/lib/modules` as a file system. Note the standard platform classes are indexed using `SYSTEM_MODULES`.

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Commit messages:
 - Cleanup.
 - 8366582: Test jdk/jshell/ToolSimpleTest.java failed: provider not found

Changes: https://git.openjdk.org/jdk/pull/27333/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27333&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8366582
  Stats: 8 lines in 2 files changed: 5 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/27333.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27333/head:pull/27333

PR: https://git.openjdk.org/jdk/pull/27333