RFR: 8311591: Add SystemModulesPlugin test case that splits module descriptors with new local variables defined by DedupSetBuilder [v5]

[Christoph]

> Add new test case with sample modules that contains some requires/exports/uses/provides.
> 
> We are just unsure if and how we should add some last step of verificaiton with the extracted and decompiled class.
> 
> Follow up task from https://github.com/openjdk/jdk/pull/14408

Christoph has updated the pull request incrementally with four additional commits since the last revision:

 - Merge remote-tracking branch 'origin/fix-8311591' into fix-8311591
   
   * origin/fix-8311591:
     Update test/jdk/tools/jlink/dedup/src/m4/p4/Main.java
     Update test/jdk/tools/jlink/dedup/src/m4/p4/Main.java
 - Update test/jdk/tools/jlink/dedup/src/m4/p4/Main.java
   
   Co-authored-by: Mandy Chung <mandy.chung at oracle.com>
 - Update test/jdk/tools/jlink/dedup/src/m4/p4/Main.java
   
   Co-authored-by: Mandy Chung <mandy.chung at oracle.com>
 - Reformat, add missing copyright header
   
   Remove duplicated module in add mods call
   
   Co-authored-by: Oliver Kopp <kopp.dev at gmail.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15234/files
  - new: https://git.openjdk.org/jdk/pull/15234/files/1a2e463e..015a3c2e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15234&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15234&range=03-04

  Stats: 35 lines in 3 files changed: 30 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/15234.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15234/head:pull/15234

PR: https://git.openjdk.org/jdk/pull/15234