METS Server: improve logging

[bertsky]

This fixes some cosmetic issues for the METS Server's log output:

• we don't need the access_log – it's quite verbose and we can always just enable the workspace debug logging instead
• we should not allow Uvicorn to initialise its own log config – but have it use our preconfigured logging facility for consistency
• the loggers should all have the same name, and to be configurable, the URL should not be part of the top-level name
• removing the UDS socket on shutdown is the normal case – no need for a warning there