Make notice compatibility routes optional

In continuation of !3402 (merged)

This patch adds a new option: :instance, :notice_compatibility_routes, which toggles on or off the notice compatibility routes for other frontends.

When making this, I struggled to figure out how to unit test it properly in the state it's currently written in. My idea was to initally just change said option to true in the config using the Pleroma.Config.put method and then change it back on_exit or to use clear_config. Neither idea worked for the frontend_static_plug_test nor the o_status_controller_test. So, I opted to unbreak the tests in their current state by simply adding said option as true to config/test.exs. If there is a better idea for how to approach this, I'm open to it.