RFR: 8249831: Test sun/security/mscapi/nonUniqueAliases/NonUniqueAliases.java is marked with @ignore

[Fernando Guallini]

The test: **sun/security/mscapi/nonUniqueAliases/NonUniqueAliases.java** relies on the `certutil.exe` tool to import and delete certificates from a keystore. It was annotated with `@ignore` due to the uncertainty of `certutil.exe` being available on the instance where the test is executed.

Rather than ignoring the test entirely, this PR updates the logic to throw a `SkippedException` if the tool is not found, ensuring the test runs when possible, and gracefully skipped otherwise.

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Commit messages:
 - Merge branch 'master' into 8249831
 - also checking exception message
 - throw skippedException is certutil is not installed

Changes: https://git.openjdk.org/jdk/pull/21305/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21305&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8249831
  Stats: 18 lines in 1 file changed: 14 ins; 2 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/21305.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21305/head:pull/21305

PR: https://git.openjdk.org/jdk/pull/21305