Add support for ACR (Azure Container Registry) and MCR (Microsoft Container Registry)

[joelverhagen]

Motivation and Context

Microsoft uses mcr.microsoft.com to host our public containers. These are syndicated to Docker Hub but image references use mcr.microsoft.com which is not currently supported by the Official MCP Registry.

See #753.

Microsoft teams want to use MCR-based images for Microsoft MCP servers.
I believe we should be adding ACR support as well, so that our customers using Azure Container Registry can use the MCP Registry as well.

In short, MCR is used for Microsoft managed containers. ACR is a solution for Azure customers to host their own containers.

How Has This Been Tested?

Unit tests.

Manual test: local push of a server.json with mcr.microsoft.com/azure-sdk/azure-mcp:2.0.0-beta.1 and azurearcjumpstart.azurecr.io/hello-arc:latest in it. The error is now about missing annotation not unsupported OCI registry.

Breaking Changes

No.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context