Add an ACP client (with the use of Mistral ACP server)

**IMPORTANT:

test best in a sandbox, if you start some agent that could do whatever it wants if it is not properly configured, Kate will not be able to hinder it

this in not reviewed yet in any way, compile and run on own risk**

This is just an experiment to see how some acp agent can generate an acp integration.

Just looking a bit at the code one already sees it did mindless copy from the lspclient plugin a lot of stuff.