RFR: 8313904: [macos] All signing tests which verifies unsigned app images are failing

[Alexander Matveev]

- This is regression from [JDK-8298488](https://bugs.openjdk.org/browse/JDK-8298488).
- Since JDK-8298488 unsigned app bundles are ad-hoc signed and `codesign` will report that app bundle is signed and thus our tests failed.
- Fixed tests by checking that all app bundles are signed and by checking how they signed ad-hoc vs actual certificate.
- Unsigned post process image will be ad-hoc re-sign when generating DMG or PKG, since we adding `.package` file which makes ad-hoc signature invalid. This is similar to [JDK-8293462](https://bugs.openjdk.org/browse/JDK-8293462).

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Commit messages:
 - 8313904: [macos] All signing tests which verifies unsigned app images are failing

Changes: https://git.openjdk.org/jdk/pull/15235/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15235&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8313904
  Stats: 94 lines in 8 files changed: 58 ins; 0 del; 36 mod
  Patch: https://git.openjdk.org/jdk/pull/15235.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15235/head:pull/15235

PR: https://git.openjdk.org/jdk/pull/15235