RFR: 8343442: Add since checker tests to the networking area modules [v3]

[Nizar Benalla]

> Can I please get a review for this patch that brings the `@since` test described [here](https://mail.openjdk.org/pipermail/jdk-dev/2024-October/009474.html) to the networking area modules.
> 
> The benefit from this is helping API authors and reviewer validate the accuracy of `@since` in their source code (and subsequently, in the generated documentation).
> 
> The test has been added for `java.base` 2 weeks ago and has helped catch some bugs before they make it to the JDK.
> 
> TIA

Nizar Benalla has updated the pull request incrementally with one additional commit since the last revision:

  Rename tests and directories under modules dir

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/21838/files
  - new: https://git.openjdk.org/jdk/pull/21838/files/1afbc91c..e30bbc5b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21838&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21838&range=01-02

  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/21838.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21838/head:pull/21838

PR: https://git.openjdk.org/jdk/pull/21838