[FEATURE REQ] Update to use MySQL flexible server in passwordless docs

[saragluna]

Is your feature request related to a problem? Please describe. MySQL flexible server has been GAed. https://learn.microsoft.com/en-us/azure/mysql/flexible-server/concepts-azure-ad-authentication. We should update all our usage of MySQL in passwordless docs from single server to flexible server.

Describe the solution you'd like

• Update the quickstart docs
  • JAVA
  • JDBC
  • JPA
• Update the migration doc
• Update the tutorial doc
• Update the reference doc
• Update the README files in sdk/jdbc/

Describe alternatives you've considered N/A

Additional context N/A

Information Checklist

• [x] Description Added
• [x] Expected solution specified

[Netyyyy]

https://github.com/MicrosoftDocs/azure-dev-docs-pr/pull/3700 https://github.com/MicrosoftDocs/azure-docs-pr/pull/214005

[Netyyyy]

close for the above PRs merged