Misc optimizations & PHP CS fixes

* better phpBb connection settings check: instead of just checking the SQL connection settings, we try to retrieve a random forum from the phpBb database
* added phpBb SQL queries log to the perfs info
* added a check for file existence in "PluginsManager#includeFileInIsolatedClosure()"
* added some "perfs.tracking" config options & renamed some existing ones
* PHP CS fixes