Implement Secure Secrets File Support for MySQL/MariaDB

[denisakp]

Enable support for loading MySQL/MariaDB client credentials (password, host, user) from the my.cnf file. This file path should be configurable in Sentinel’s configuration and loaded at runtime.

More details here

Acceptance Criteria:

• MySQL/MariaDB connections retrieve credentials from my.cnf file;
• if the file is missing, Sentinel falls back to alternative input methods.