Running `FastMCP()` overwrites global logging configuration

[mithaler]

Describe the bug
Running FastMCP() calls configure_logging, which overwrites the global logging config. This makes it difficult to integrate it into other frameworks built on FastAPI via mounting, especially in complex apps that need to set up their logs in a specific way.

To Reproduce
Follow the example mounting a FastMCP instance in an existing FastAPI server on the top-level README, in an app with any kind of existing logging config.

Expected behavior
FastMCP should not do this, or at the very least it should make it possible to disable or overwrite this behavior.

[olejorgenb]

Duplicate of #420