RFR: 8350601: Miscellaneous updates to jpackage test lib [v4]

[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).

Alexey Semenyuk has updated the pull request incrementally with one additional commit since the last revision:

  Better exception message

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23754/files
  - new: https://git.openjdk.org/jdk/pull/23754/files/71072247..2e538caf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23754&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23754&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 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