Adopt a PHP Library

Had a first attempt at this over at https://git.drupalcode.org/project/mcp_client/-/merge_requests/1 . It seems the Drupal request out to the MCP servers is broken. Still need to investigate.

The PHP library also supports SSE, STDIO, or HTTP requests, so we should likely add that as options in the MCP entity type.

@robloach - I think https://github.com/symfony/mcp-sdk will be more interesting going forward, if they keep up the work.