RFR: 8342576: [macos] AppContentTest still fails after JDK-8341443 for same reason on older macOS versions

[Alexander Matveev]

- It is not clear on which macOS versions codesign fails if application bundle contains additional content.
- As a result test was modified to generate only application image, since PKG or DMG cannot be generated if signing fails. Exit code of jpackage is ignored, but generated application image will be checked for additional content.
- This change is for macOS only.
- Previous implementation of test (forcing expected exist code to 1) was not doing anything useful, since we never checked if additional content was copied or not.

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Commit messages:
 - 8342576: [macos] AppContentTest still fails after JDK-8341443 for same reason on older macOS versions

Changes: https://git.openjdk.org/jdk/pull/21698/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21698&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342576
  Stats: 82 lines in 2 files changed: 56 ins; 16 del; 10 mod
  Patch: https://git.openjdk.org/jdk/pull/21698.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21698/head:pull/21698

PR: https://git.openjdk.org/jdk/pull/21698