Fine graned control of the file watcher - avoid unnecessary reloads

[pieroit]

Currently the watcher makes the cat restart each time any python file changes, so:

• when a developer changes a file (this is ok)
• when a plugin is installed / uninstalled (this is not ok)

Also this line excludes reload for files in the test suite. I wanted to exclude the whole test folder, but did not manage to do it.

Solution: take more control of the watcher and activate/deativate only when necessary and only on the necessary folders

• WatchFiles in FastAPI
• WatchFiles docs