localserve: change queue to deliver to localserve smtp server

instead of skipping on any smtp and delivering messages to accounts.
we dial the ip of the smtp listener, which is localhost:1025 by default.

the smtp server now uses a mock dns resolver during spf & dkim verification for
hosted domains (localhost by default), so they should pass.

the advantage is that we get regular full smtp server behaviour for delivering
in localserve, including webhooks, and potential first-time sender delays
(though this is disabled by default now).

incoming deliveries now go through normal address resolution, where before we
would always deliver to mox@localhost. we still accept email for unknown
recipients to mox@localhost.

this will be useful upcoming alias/list functionality.

localserve will now generate a dkim key when creating a new config. existing
users may wish to reset (remove) their localserve directory, or add a dkim key.

mox-/admin.go

@@ -99,7 +99,7 @@ func dkimKeyNote(kind string, selector, domain dns.Domain) string {
 	return s
 }
 
-// MakeDKIMEd25519Key returns a PEM buffer containing an rsa key for use with
+// MakeDKIMRSAKey returns a PEM buffer containing an rsa key for use with
 // DKIM.
 // selector and domain can be empty. If not, they are used in the note.
 func MakeDKIMRSAKey(selector, domain dns.Domain) ([]byte, error) {