RFR: 8322657: CDS filemap fastdebug assert while loading Graal CE Polyglot in isolated classloader

[Calvin Cheung]

Please review this small fix for skipping the non-existent `SharedClassPathEntry` in `FileMapInfo::get_module_shared_path_index`.
Please refer to the bug report for more details.

Passed tiers 1 - 4 testing, including the new test.

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Commit messages:
 - 8322657: CDS filemap fastdebug assert while loading Graal CE Polyglot in isolated classloader

Changes: https://git.openjdk.org/jdk/pull/17275/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17275&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8322657
  Stats: 188 lines in 6 files changed: 179 ins; 0 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/17275.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17275/head:pull/17275

PR: https://git.openjdk.org/jdk/pull/17275