Add ProxySQL MariaDB & XtraDB Galera Doc, Update MySQL doc

[Neaj-Morshad-101]

No description provided.

[github-actions]

Visit the preview URL for this PR (updated for commit 82c0ddd):

https://kubedb-v2-hugo--pr749-proxy-1f2u7q4b.web.app

_{(expires Wed, 30 Apr 2025 09:20:00 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}

_{Sign: 0f29ae8ae0bd54a99bf2b223b6833be47acd5943}

[gitguardian]

⚠️ GitGuardian has uncovered 1 secret following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secret in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
5161057	Triggered	RSA Private Key	b8dee67	docs/guides/proxysql/backends/xtradb-galera/external/index.md	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secret safely. Learn here the best practices.
3. Revoke and rotate this secret.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

---

^{🦉 GitGuardian detects secrets in your source code to help developers and security teams secure the modern development process. You are seeing this because you or someone else with access to this repository has authorized GitGuardian to scan your pull request.}

[sheikh-arman]

add side bar menu for the https://kubedb-v2-hugo--pr749-proxy-1f2u7q4b.web.app/docs/v2025.3.24/guides/proxysql/backends/mysqlgrp/

[sheikh-arman]

lgtm