[PS] Migrate MySQL module to autorest v4

[JoyerJin]

Description

Mandatory Checklist

• Please choose the target release of Azure PowerShell. (⚠️Target release is a different concept from API readiness. Please click below links for details.)

  • General release
  • Public preview
  • Private preview
  • Engineering build
  • No need for a release

• Check this box to confirm: I have read the Submitting Changes section of CONTRIBUTING.md and reviewed the following information:

• SHOULD update ChangeLog.md file(s) appropriately
  • Update src/{{SERVICE}}/{{SERVICE}}/ChangeLog.md.
    • A snippet outlining the change(s) made in the PR should be written under the ## Upcoming Release header in the past tense.
  • Should not change ChangeLog.md if no new release is required, such as fixing test case only.
• SHOULD regenerate markdown help files if there is cmdlet API change. Instruction
• SHOULD have proper test coverage for changes in pull request.
• SHOULD NOT adjust version of module manually in pull request

[azure-client-tools-bot-prd]

Thanks for your contribution! The pull request validation has started. Please revisit this comment for updated status.

[Copilot]

Pull Request Overview

This pull request removes support for Azure Database for MySQL single-server cmdlets and focuses exclusively on Azure Database for MySQL flexible servers. This is a breaking change that removes approximately 20+ legacy cmdlets and introduces several improvements for flexible server management.

Key changes:

• Removed all single-server cmdlets (e.g., Get-AzMySqlServer, New-AzMySqlServer, Update-AzMySqlConfiguration)
• Retained and updated flexible server cmdlets
• Updated module dependencies, output types, and parameter types
• Added breaking change exception file with 102 documented breaking changes
• Updated help documentation and tests

Reviewed Changes

Copilot reviewed 138 out of 217 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/MySql/MySql/ChangeLog.md	Added breaking change notice with reference link
src/MySql/MySql/Az.MySql.psd1	Removed single-server cmdlets from exports; updated Az.Accounts dependency to 5.3.0
tools/StaticAnalysis/Exceptions/Az.MySql/BreakingChangeIssues.csv	Added 102 breaking change exception entries documenting removed cmdlets and API changes
Multiple help files	Removed documentation for single-server cmdlets; updated output types for flexible server cmdlets
Test files	Removed tests for single-server cmdlets; updated flexible server test scenarios
src/MySql/MySql.Autorest/test/utils.ps1	Simplified test setup; improved password handling
Various .md files	Updated parameter types from enums to strings; removed "To construct" notes for InputObject parameters

[Copilot]

The changelog entry is too vague for users. It should explicitly state that single-server cmdlets have been removed and list the major breaking changes. Users need to understand what specific cmdlets are no longer available and what alternatives they should use. Consider adding bullet points listing the removed cmdlet categories (e.g., "Removed single-server cmdlets: Get-AzMySqlServer, New-AzMySqlServer, Update-AzMySqlConfiguration, etc.") and guidance to migrate to flexible server cmdlets.