Add methods to track and verify client capabilities during initialization. This
includes storing client parameters from the initialize request and providing a
check_client_capability method to verify if specific capabilities are supported
by the connected client.
We currently return a generic instance of RequestContext without
a specialization on the Session type. This makes it impossible
for servers to typesafe call `list_roots()` and other methods.
We now return a specific instance of `RequestContext[ServerSession]`
We will be a bit more low level and expect callees to import mcp.types
instead of relying in re-exported types. This makes usage more explicit
and avoids potential collisions in mcp.server.
The helper types in mcp.server.types got really confusioning during
implementation as they overlapped with mcp.types. I now believe it
is better if we stay more low level to the spec types.
To do this, we now only use mcp.types everywhere. We renamed mcp.server.types
to mcp.server.models and removed it to the absolute minimum.
