RFR: 8350601: Miscellaneous updates to jpackage test lib

[Alexey Semenyuk]

- Unify TKit.createTempDirectory() and TKit.createTempFile() functions. Remove `throws IOexception` from their signatures. Add relevant tests.
 - JPackageCommand.java: remove try/catch(IOexception) around `TKit.createTempDirectory()` call.
 - AppImagePackageTest.java: replace `TKit.createTempDirectory(null)` with `TKit.createTempDirectory("appimage")` to fix NPE.
 - Make `TKit.assertDirectoryExists(Path, Optional<Boolean>)` private. This is internal and shouldn't be exposed.
 - add `TKit.assertEquals(boolean, boolean)` and `TKit.assertNotEquals(boolean, boolean)` with tests.
 - AdditionalLauncher.java: remove redundant code duplicating functionality of `TKit.createTempFile()` (should have been cleaned long ago).
 - JPackageCommand.java: add a check for the main jar in the app image if the main jar was specified. Missing part of [JDK-8325089](https://bugs.openjdk.org/browse/JDK-8325089).

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

Commit messages:
 - Better test description and add tests for roles with dots
 - Merge branch 'master' into decouple-tkit
 - Test if the main jar is in the app image if specified.
 - Merge branch 'decouple-executor-result' into decouple-tkit
 - Merge branch 'decouple-fix-annotations' into decouple-executor-result
 - Fix javac error
 - Merge branch 'decouple-junit' into decouple-fix-annotations
 - Merge branch 'master' into decouple-junit
 - Remove redundant "return"
 - Fix merge
 - ... and 23 more: https://git.openjdk.org/jdk/compare/dfcd0df6...01fa2528

Changes: https://git.openjdk.org/jdk/pull/23754/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23754&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8350601
  Stats: 251 lines in 5 files changed: 199 ins; 26 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/23754.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23754/head:pull/23754

PR: https://git.openjdk.org/jdk/pull/23754