[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/federator.go

@@ -37,7 +37,7 @@ var _ interface {
 
 type Federator struct {
 	db           db.DB
-	federatingDB federatingdb.DB
+	federatingDB *federatingdb.DB
 	clock        pub.Clock
 	converter    *typeutils.Converter
 	transport    transport.Controller
@@ -54,7 +54,7 @@ type Federator struct {
 // NewFederator returns a new federator instance.
 func NewFederator(
 	state *state.State,
-	federatingDB federatingdb.DB,
+	federatingDB *federatingdb.DB,
 	transportController transport.Controller,
 	converter *typeutils.Converter,
 	visFilter *visibility.Filter,
@@ -112,7 +112,7 @@ func (f *Federator) FederatingActor() pub.FederatingActor {
 }
 
 // FederatingDB returns the underlying FederatingDB interface.
-func (f *Federator) FederatingDB() federatingdb.DB {
+func (f *Federator) FederatingDB() *federatingdb.DB {
 	return f.federatingDB
 }