### What problem does this PR solve?
Add MCP treamable-http transport.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Add mcp self-host mode, a complement of #7084.
### Type of change
- [x] New Feature (non-breaking change which adds functionality)
### What problem does this PR solve?
Add MCP support with a client example.
Issue link: #4344
### Type of change
- [x] New Feature (non-breaking change which adds functionality)