RFR: 8364587: Update jpackage internal javadoc

[Alexey Semenyuk]

Fix javadoc errors in DefaultLauncherIcon, Launcher, and Application classes. Additionally, add javadoc to some methods of PackagingPipeline class.

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Commit messages:
 - DefaultLauncherIcon: minor javadoc fix
 - Add javadoc to PackagingPipeline
 - Launcher, Application: fix javadoc

Changes: https://git.openjdk.org/jdk/pull/26609/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26609&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364587
  Stats: 35 lines in 4 files changed: 30 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/26609.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26609/head:pull/26609

PR: https://git.openjdk.org/jdk/pull/26609