RFR: 8341939: SigningOptionsTest fails without Xcode with command line developer tools after JDK-8341443

[Alexander Matveev]

- Removed hard check for "Xcode with command line developer tools" when `--mac-sign` is specified and instead we will show information message if `codesign` fails for any reason that possible root cause of failure is missing Xcode with command line developer tools.
- Reason for this is that `codesign` works fine on recent macOS versions and it looks like dependency on Xcode with command line developer tools is no longer required. Unfortunately it is unknown which macOS versions are require Xcode with command line developer tools in order to `codesign` work, so this check will be done as soft check.
- SigningOptionsTest which requires "Xcode with command line developer tools" on some older macOS versions was modified to skip certain tests which might fail if Xcode is not installed.

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Commit messages:
 - Merge remote-tracking branch 'upstream/master' into JDK-8341939
 - 8341939: SigningOptionsTest fails without Xcode with command line developer tools after JDK-8341443

Changes: https://git.openjdk.org/jdk/pull/21628/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21628&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341939
  Stats: 96 lines in 8 files changed: 62 ins; 26 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/21628.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21628/head:pull/21628

PR: https://git.openjdk.org/jdk/pull/21628