vectorstores: Add MariaDB

[Simoffsky]

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[Simoffsky]

I noticed that a similar MariaDB integration PR.

However, I started working on mine a week ago and took extra time to ensure tests and features were complete. My PR introduces several improvements:

• Delete by filters
• Document updates (using prepared SQL statements)
• Advanced filtering (e.g., <, !=, =)
• HNSW index configuration support
• Example included