Replace beego/orm with dbx (#2693)

* Start migration to dbx package

* Fix annotations and bookmarks bindings

* Fix tests

* Fix more tests

* Remove remaining references to beego/orm

* Add PostScanner/PostMapper interfaces

* Fix importing SmartPlaylists

* Renaming

* More renaming

* Fix artist DB mapping

* Fix playlist updates

* Remove bookmarks at the end of the test

* Remove remaining `orm` struct tags

* Fix user timestamps DB access

* Fix smart playlist evaluated_at DB access

* Fix search3

model/transcoding.go

@@ -1,7 +1,7 @@
 package model
 
 type Transcoding struct {
-	ID             string `structs:"id" json:"id"            orm:"column(id)"`
+	ID             string `structs:"id" json:"id"`
 	Name           string `structs:"name" json:"name"`
 	TargetFormat   string `structs:"target_format" json:"targetFormat"`
 	Command        string `structs:"command" json:"command"`