feat(build): improve lint-locale-usage further (#8736)

Print out a list of all unused msgids
Handle Go files that make calls to translation.
Handle `models/unit/unit.go`, which stores msgids in `$Unit.NameKey`
Handle .locale.Tr in templates
Handle simple dynamically constructed `Tr("msgid-prefix." + SomeFunctionCall())`.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8736
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Ellen Εμιλία Άννα Zscheile <fogti+devel@ytrizja.de>
Co-committed-by: Ellen Εμιλία Άννα Zscheile <fogti+devel@ytrizja.de>

models/asymkey/gpg_key_object_verification.go

@@ -36,6 +36,7 @@ type ObjectVerification struct {
 	TrustStatus    string
 }
 
+// llu:TrKeys
 const (
 	// BadSignature is used as the reason when the signature has a KeyID that is in the db
 	// but no key that has that ID verifies the signature. This is a suspicious failure.