Add docs for jvm_artifacts target generator

[grihabor]

Add docs for the jvm_artifacts target implemented in #20336

[huonw]

I've assumed that this doesn't require release notes, but feel free to add some if it's worth calling out!

[grihabor]

@huonw Yeah, I can add a line 5b956fe

[WorkerPants]

I tried to automatically cherry-pick this change back to each relevant milestone, so that it is available in those older releases of Pants.

❌ 2.20.x

I was unable to cherry-pick this PR to 2.20.x, likely due to merge-conflicts.

Steps to Cherry-Pick locally

To resolve:

1. (Ensure your git working directory is clean)
2. Run the following script to reproduce the merge-conflicts:

   git fetch https://github.com/pantsbuild/pants main \
     && git fetch https://github.com/pantsbuild/pants 2.20.x \
     && git checkout -b cherry-pick-20890-to-2.20.x FETCH_HEAD \
     && git cherry-pick 4012d9eff25e6913a32623863f2b646c27fa7e10

3. Fix the merge conflicts and commit the changes
4. Run build-support/cherry_pick/make_pr.sh "20890" "2.20.x"

Please note that I cannot re-run CI if a job fails. Please work with your PR approver(s) to re-run CI if necessary.

❌ 2.21.x

I was unable to cherry-pick this PR to 2.21.x, likely due to merge-conflicts.

Steps to Cherry-Pick locally

To resolve:

1. (Ensure your git working directory is clean)
2. Run the following script to reproduce the merge-conflicts:

   git fetch https://github.com/pantsbuild/pants main \
     && git fetch https://github.com/pantsbuild/pants 2.21.x \
     && git checkout -b cherry-pick-20890-to-2.21.x FETCH_HEAD \
     && git cherry-pick 4012d9eff25e6913a32623863f2b646c27fa7e10

3. Fix the merge conflicts and commit the changes
4. Run build-support/cherry_pick/make_pr.sh "20890" "2.21.x"

Please note that I cannot re-run CI if a job fails. Please work with your PR approver(s) to re-run CI if necessary.

---

When you're done manually cherry-picking, please remove the needs-cherrypick label on this PR.

Thanks again for your contributions!

🤖 Beep Boop here's my run link

[grihabor]

@benjyw I have permission problems with build-support/cherry_pick/make_pr.sh, could you please fix the cherry-pick?
You only need to git rm docs/notes/2.22.x.md

Or I could create a completely separate pr

[grihabor]

I got it working:

• Add docs for jvm_artifacts target generator (Cherry-pick of #20890) #20920
• Add docs for jvm_artifacts target generator (Cherry-pick of #20890) #20919