feat(mcp-core): support Mcp-Name header for Streamable HTTP (SEP-2243)

[cooleditphoto]

Add MCP_NAME header constant and inject it in the streamable HTTP client transport (HttpClientStreamableHttpTransport) and HTTP server transport

Motivation and Context

#990
To solve the Mcp_Name part of https://modelcontextprotocol.io/seps/2243-http-standardization

How Has This Been Tested?

[INFO] BUILD SUCCESS
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[INFO] Total time: 04:44 min
[INFO] Finished at: 2026-06-02T09:02:38-04:00
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Breaking Changes

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