Propagate version from fastmcp to _mcp_server, add test for clientInfo

[yannj-fr]

Propage version from FastMCP layer to the _mcp_server. Currently the version can not be set and will fallback for mcp package version.

Motivation and Context

I believe it make sense to have the version correctly.

How Has This Been Tested?

Tested end to end, tests added in test suite

Breaking Changes

N/A

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