[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/federation/federatingdb/owns.go

@@ -34,7 +34,7 @@ import (
 // Owns returns true if the IRI belongs to this instance, and if
 // the database has an entry for the IRI.
 // The library makes this call only after acquiring a lock first.
-func (f *federatingDB) Owns(ctx context.Context, id *url.URL) (bool, error) {
+func (f *DB) Owns(ctx context.Context, id *url.URL) (bool, error) {
 	log.DebugKV(ctx, "id", id)
 
 	// if the id host isn't this instance host, we don't own this IRI
@@ -150,7 +150,7 @@ func (f *federatingDB) Owns(ctx context.Context, id *url.URL) (bool, error) {
 	return false, fmt.Errorf("could not match activityID: %s", id.String())
 }
 
-func (f *federatingDB) ownsLike(ctx context.Context, uri *url.URL) (bool, error) {
+func (f *DB) ownsLike(ctx context.Context, uri *url.URL) (bool, error) {
 	username, id, err := uris.ParseLikedPath(uri)
 	if err != nil {
 		return false, fmt.Errorf("error parsing Like path for url %s: %w", uri.String(), err)