Remove most behaviour disparities between blocks and mutes (#7231)

* Remove most behaviour disparities between blocks and mutes

The only differences between block and mute should be:

- Mutes can optionally NOT affect notifications
- Mutes should not be visible to the muted

Fix #7230
Fix #5713

* Do not allow boosting someone you blocked

Fix #7248

* Do not allow favouriting someone you blocked

* Fix nil error in StatusPolicy