RFR: 8377857: Add since checker test for java.naming module

[Jaikiran Pai]

Can I please get a review of this change which introduces a test to verify the usages of `@since` javadoc tags in the `java.naming` module? This addresses https://bugs.openjdk.org/browse/JDK-8377857.

The `SinceChecker` test utility has been in use for several modules, but wasn't added for java.naming. The commit in this PR adds one for that module.

The `SinceChecker` test utility does not handle the presence of a comma in (for example `@since X, Y`) correctly. The javadoc tag spec for `@since` allows that syntax https://docs.oracle.com/en/java/javase/25/docs/specs/javadoc/doc-comment-spec.html#since. As a workaround, the commit in this PR splits the `@since` on `javax.naming.InitialContext` class into two separate declarations (this too is allowed by the `@since` tag spec). I've verified that the generated javadoc continues to correctly show these values. I have also spoken to Nizar about this issue in SinceChecker and it will be addressed separately.

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Commit messages:
 - 8377857: Add since checker test for java.naming module

Changes: https://git.openjdk.org/jdk/pull/29705/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29705&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8377857
  Stats: 32 lines in 2 files changed: 30 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/29705.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29705/head:pull/29705

PR: https://git.openjdk.org/jdk/pull/29705