Don't automatically setup the filesystem the moment we load OC\Files\Filesystem

Currently the filesystem is setup the moment `OC\Files\Filesystem` is first mentioned, this can leads to an unpredictable state since the order of initializing owncloud is dependent on apps that might or might not accidentally setup the filesystem (i.e. using one of the `Filesystem::` constants while setting up hooks).

This PR changes it to explicitly setup the filesystem either after loading all apps or after a successful login and ensures we load our components in the order we expect.

cc @DeepDiver1975 @PVince81 @butonic