RFR: 8317634: Introduce the ability to exclude modules from dedup-legal-notices plugin of jlink

[Jaikiran Pai]

Can I please get a review of this change which proposes to implement the enhancement request noted in https://bugs.openjdk.org/browse/JDK-8317634?

The change in this commit introduces a new `exclude-modules` argument to the `dedup-legal-notices` jlink plugin. This optional argument takes a comma separated values of module names. These module names are then excluded from the de-duplication of license notice files during image generation.

Two new test methods have been added to the existing `LegalFilePluginTest` jtreg test case to verify this implementation. Existing tests in `test/jdk/tools/jlink` continue to pass. tier testing is currently in progress.

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Commit messages:
 - introduce an argument for --dedup-legal-notices option of jlink to optionally exclude certain modules' license files from de-duplication

Changes: https://git.openjdk.org/jdk/pull/16066/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16066&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317634
  Stats: 168 lines in 2 files changed: 161 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/16066.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16066/head:pull/16066

PR: https://git.openjdk.org/jdk/pull/16066