mute: integrate new MutelistManager

This patch is slightly large (I think still within the guidelines tho) ,
but also pretty straightforward. I thought for a while about how I could
split this up in a straightforward way, and I couldn’t come up with
anything without breaking intermediate builds.

- Deleted a lot of old/unnecessary code (ie. the Collection extension
  for MuteItem, since we’re now using the MutelistManager sets)

- Changed damus_state.contacts to damus_state.mutelist_manager for all
  mute list manager work

- Updated MutelistView to take advantage of new code (this is probably
  the largest change in this patch)

Lighting-Address: fishcharlie@strike.me
Signed-off-by: Charlie Fish <contact@charlie.fish>
Reviewed-by: William Casarin <jb55@jb55.com>
Link: 20240210163650.42884-4-contact@charlie.fish
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Views/Muting/AddMuteItemView.swift

@@ -72,7 +72,7 @@ struct AddMuteItemView: View {
 
                 // Actually update & relay the new mute list
                 if let mute_item {
-                    let existing_mutelist = state.contacts.mutelist
+                    let existing_mutelist = state.mutelist_manager.event
 
                     guard
                         let full_keypair = state.keypair.to_full(),
@@ -81,7 +81,7 @@ struct AddMuteItemView: View {
                         return
                     }
 
-                    state.contacts.set_mutelist(mutelist)
+                    state.mutelist_manager.set_mutelist(mutelist)
                     state.postbox.send(mutelist)
                 }