RFR: 8342576: [macos] AppContentTest still fails after JDK-8341443 for same reason on older macOS versions [v2]

[Alexey Semenyuk]

> Change suffixes produced by `TKit.createUniqueFileName()` function from `.<NUM>` to `-<NUM>` (e.g.: from `.0` to `-0`).
> Apple's `codesign` tool can't sign directories with periods in their names as it interprets them as bundles. Directories produced by `TKit.createUniqueFileName()` may end up in an app image and become a subject for signing if used with `--app-content` jpackage parameter

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

  Rework test to copy `--app-content` into "Contents/Resources" folder instead of "Contents" on OSX.

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21741/files
  - new: https://git.openjdk.org/jdk/pull/21741/files/a7bda48b..9351654f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21741&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21741&range=00-01

  Stats: 90 lines in 1 file changed: 73 ins; 5 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/21741.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21741/head:pull/21741

PR: https://git.openjdk.org/jdk/pull/21741