Remove AutoRest across generators, IDE surfaces, validation assets, and docs

[Copilot]

This removes AutoRest after the deprecation window by deleting it as a supported generator everywhere it was still wired in: core/CLI code paths, IDE integrations, validation assets, generated-code fixtures, and user-facing documentation. The remaining surfaces now consistently present NSwag, OpenAPI Generator, Swagger Codegen, Kiota, Refitter, and the migration guide for former AutoRest users.

• Core + CLI removal

  • Removed SupportedCodeGenerator.AutoRest and SupportedCodeGenerator.AutoRestV3
  • Deleted AutoRest generator/options implementations, dependency installer hooks, package dependency mappings, and external tool registration
  • Removed the csharp autorest CLI command and related factory/DI registrations

• IDE surface cleanup

  • Removed AutoRest from VSIX, VS Code, Visual Studio for Mac, and IntelliJ menus, command registrations, factories, manifests, and settings
  • Deleted AutoRest-specific custom tool handlers and option pages

• Tests + fixtures cleanup

  • Deleted AutoRest-specific unit/integration tests and project includes
  • Removed AutoRest generated-code fixture trees and solution entries
  • Updated remaining tests to assert absence where relevant instead of deprecation behavior

• Validation + workflow updates

  • Removed AutoRest from workflow matrices, smoke/regression/production generation steps, and helper PowerShell utilities
  • Dropped obsolete publish metadata/tags and ignore entries tied to AutoRest outputs

• Documentation + release notes

  • Removed AutoRest from README, marketplace docs, website pages, VS Code docs, CLI docs, and generated-code guidance
  • Updated docs/AutoRestMigration.md to describe post-removal migration rather than pending deprecation
  • Added an Unreleased changelog entry for the removal

Example of the public surface change:

public enum SupportedCodeGenerator
{
    NSwag = 0,
    NSwagStudio = 1,
    Swagger = 3,
    OpenApi = 4,
    Kiota = 6,
    Refitter = 7
}

[sonarqubecloud]

Quality Gate failed

Failed conditions
0.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud