[chore] various federatingdb tweaks (#4178)

after seeing a potential reported federating worker lockup i decided to start digging into the federatingdb code. this PR encompasses:
- removes one of our last unused interface types `federatingdb.DB{}`, replacing it with a struct type `*federatingdb.DB{}`
- in `transport.dereferenceLocal()` differentiates between an unsupported lookup type and ErrNoEntries to reduce unnecessary calls, and reduce potential lockups that may occur while trying to call our own endpoints that then call `federatingdb.Lock()`
- removes a bunch of the locks on follow state changes since the DB already synchronizes that
- removes the unnecessary `pub.Clock{}` struct field and type passed to the transport controller

frankly it would be great if we could remove the locking in `federatingdb.Lock()` and instead handle it ourselves as it gets very confusing trying to figure out what functions will have locks held. but i guess that's one for when we move further away from the go-fed/activity/pub package usage.

Reviewed-on: https://codeberg.org/superseriousbusiness/gotosocial/pulls/4178
Co-authored-by: kim <grufwub@gmail.com>
Co-committed-by: kim <grufwub@gmail.com>

internal/processing/workers/fromfediapi_move.go

@@ -269,9 +269,8 @@ func (p *fediAPI) MoveAccount(ctx context.Context, fMsg *messages.FromFediAPI) e
 	// try to send the same Move several times with
 	// different IDs (you never know), but we only
 	// want to process them based on origin + target.
-	unlock := p.state.FedLocks.Lock(
-		"move:" + originAcctURIStr + ":" + targetAcctURIStr,
-	)
+	key := "move:" + originAcctURIStr + ":" + targetAcctURIStr
+	unlock := p.state.FedLocks.Lock(key)
 	defer unlock()
 
 	// Check if Move is rate limited based