RFR: 8358723: jpackage signing issues: the main launcher doesn't have entitlements

[Alexey Semenyuk]

Fix the regression introduced by [JDK-8333664](https://bugs.openjdk.org/browse/JDK-8333664) that jpackage was not using entitlements when signing directories. This gave the main launcher no entitlements.

Additionally, enhance `jdk.jpackage.internal.util.PListReader` class.

Test code will verify that all launchers have the entitlements when `--mac-sign` is used or when a predefined app image is signed.

Ensured signing tests failed without the fix to `AppImageSigner.java` and that they passed with the fix.

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Commit messages:
 - Strip trailing whitespace
 - Follow up to PListReader changes
 - PListReader: add queryDictValue(); update javadoc
 - Add extra test cases
 - Applied blessed-modifier-order.sh
 - Update PListReader
 - Need to access jdk.jpackage/jdk.jpackage.internal.resources.ResourceLocator from tests
 - Verify launchers have entitlements when app is signed.
 - Enhance PListReader
 - Enhance PListReader.

Changes: https://git.openjdk.org/jdk/pull/27493/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27493&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8358723
  Stats: 610 lines in 10 files changed: 547 ins; 8 del; 55 mod
  Patch: https://git.openjdk.org/jdk/pull/27493.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27493/head:pull/27493

PR: https://git.openjdk.org/jdk/pull/27493