Remove xunit trait attributes and update new-command documentation

[hallipr]

What does this PR do?

In the migration to servers/ and tools/, the use of [Trait()] attributes to separate tests for different tools and differentiate live tests from unit tests was replaced with simpler project path matching. The documentation was never updated to reflect this and the traits were gradually added back to some test classes. This PR removes the traits and updates the docs.

GitHub issue number?

[Link to the GitHub issue this PR addresses]

Pre-merge Checklist

• [ ] Required for All PRs
  • [ ] Read contribution guidelines
  • [ ] PR title clearly describes the change
  • [ ] Commit history is clean with descriptive messages (cleanup guide)
  • [ ] Added comprehensive tests for new/modified functionality
  • [ ] Updated servers/Azure.Mcp.Server/CHANGELOG.md and/or servers/Fabric.Mcp.Server/CHANGELOG.md for product changes (features, bug fixes, UI/UX, updated dependencies)
• [ ] For MCP tool changes:
  • [ ] One tool per PR: This PR adds or modifies only one MCP tool for faster review cycles
  • [ ] Updated servers/Azure.Mcp.Server/README.md and/or servers/Fabric.Mcp.Server/README.md documentation
  • [ ] Validate README.md changes using script at eng/scripts/Process-PackageReadMe.ps1. See Package README
  • [ ] Updated command list in /servers/Azure.Mcp.Server/docs/azmcp-commands.md and/or /docs/fabric-commands.md
  • [ ] Run .\eng\scripts\Update-AzCommandsMetadata.ps1 to update tool metadata in azmcp-commands.md (required for CI)
  • [ ] For new or modified tool descriptions, ran ToolDescriptionEvaluator and obtained a score of 0.4 or more and a top 3 ranking for all related test prompts
  • [ ] For new tools associated with Azure services or publicly available tools/APIs/products, add URL to documentation in the PR description
• [ ] Extra steps for Azure MCP Server tool changes:
  • [ ] Updated test prompts in /servers/Azure.Mcp.Server/docs/e2eTestPrompts.md
  • [ ] 👉 For Community (non-Microsoft team member) PRs:
    • [ ] Security review: Reviewed code for security vulnerabilities, malicious code, or suspicious activities before running tests (crypto mining, spam, data exfiltration, etc.)
    • [ ] Manual tests run: added comment /azp run mcp - pullrequest - live to run Live Test Pipeline