feat: Add support for MCP discovery

[alecswan]

It would be great to enable dynamic discovery and registration of MCP servers.
One way to implement this is by adding support for MCP Endpoints in LiteLLM.
LiteLLM allows listing MCPs available as well as invoking a particular MCP.

[MathurAditya724]

IMHO, I believe this is out of scope for inspector but we are working on a proxy interface which does this.