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