[Docs] 3.8.1 release

[catalinaadam]

Ticket number: PMM-0

Feature build: SUBMODULES-0

If this PR adds, removes or alters one or more API endpoints, please review and update the relevant API documentation as well:

• API Docs updated

If this PR is related to other PRs, contributions, or ongoing work in this or other repositories, please reference them here:

• Merged v3 into doc-3.8.1 to resolve merge conflicts in release-notes navigation/config files while keeping the 3.8.1 release notes update.

[it-percona-cla]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you all sign our Contributor License Agreement before we can accept your contribution.
2 out of 4 committers have signed the CLA.

✅ ademidoff
✅ catalinaadam
❌ Copilot
❌ aaron-percona
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[Copilot]

@copilot resolve the merge conflicts in this pull request

Done — I resolved the merge conflicts by merging v3 into this branch in commit 184168878.