PLT-3695 refactoring to use sql_upgrader (#3788)

* PLT-3695 unitying upgrade support

* PLT-3695 refactoring to use sql_upgrader

* Fixing unit test

* Adding 3.3 to 3.4

* Fixing upgrading

* Seperating DB schema from version.go

* Fixing upgrade cmd

* Moving to const for exit codes

* remving old unused code

store/sql_session_store.go

@@ -29,14 +29,6 @@ func NewSqlSessionStore(sqlStore *SqlStore) SessionStore {
 	return us
 }
 
-func (me SqlSessionStore) UpgradeSchemaIfNeeded() {
-	// ADDED for 2.1 REMOVE for 2.5
-	deviceIdLength := me.GetMaxLengthOfColumnIfExists("Sessions", "DeviceId")
-	if len(deviceIdLength) > 0 && deviceIdLength != "512" {
-		me.AlterColumnTypeIfExists("Sessions", "DeviceId", "VARCHAR(512)", "VARCHAR(512)")
-	}
-}
-
 func (me SqlSessionStore) CreateIndexesIfNotExists() {
 	me.CreateIndexIfNotExists("idx_sessions_user_id", "Sessions", "UserId")
 	me.CreateIndexIfNotExists("idx_sessions_token", "Sessions", "Token")