RFR: 8349564: Clean warnings found in jpackage tests when building them with -Xlint:all

[Alexey Semenyuk]

Clean warnings found in jpackage tests when building them with `-Xlint:all` option in Eclipse IDE. 

They are:
 - redundant imports (solution: remove)
 - unused function/fields (solution: remove)
 - missing SuppressWarnings-s (solution: add what is missing)
 - redundant SuppressWarnings-s (solution: remove)
 - raw types used (solution: use wildcard or more specific types if appropriate)
 - generic varargs (solution: convert to single/double/list arguments)
 - an incomplete list of enum elements in switch statements (solution: add `default` branch)

To prevent regression, added `-Xlint:all -Werror` to the compiler command line of all jpackage tests

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

Commit messages:
 - Update copyright year
 - Add -Xlint:all and -Werror args to compiler command line of all jpackage tests
 - Bad merge fix
 - Merge branch 'master' into jlint-tests
 - Copyright year updated
 - Undo jlint clean up for the implementation
 - More jlint errors fixed
 - Merge branch 'master' into jlint-tests
 - "Cleanup" bugfix. Double facepalm
 - Merge branch 'master' into jlint-tests
 - ... and 3 more: https://git.openjdk.org/jdk/compare/eb847026...47217bb3

Changes: https://git.openjdk.org/jdk/pull/23455/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23455&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349564
  Stats: 346 lines in 82 files changed: 68 ins; 51 del; 227 mod
  Patch: https://git.openjdk.org/jdk/pull/23455.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23455/head:pull/23455

PR: https://git.openjdk.org/jdk/pull/23455