RFR: 8360571: Description of launchers is lost in two phase packaging

[Alexey Semenyuk]

Store launcher descriptions in `.jpackage.xml` file so that they don't get lost in two-step packaging

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Commit messages:
 - 8360571: Description of launchers is lost in two phase packaging

Changes: https://git.openjdk.org/jdk/pull/28436/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28436&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8360571
  Stats: 97 lines in 6 files changed: 74 ins; 12 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/28436.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28436/head:pull/28436

PR: https://git.openjdk.org/jdk/pull/28436