Fix incorrect action duration time when rerun the job before executed once (#28364)

Fix #28323
Reason was mentioned here:
https://github.com/go-gitea/gitea/issues/28323#issuecomment-1841867298

### Changes: (maybe breaking)
We can rerun jobs in Gitea, so there will be some problems in
calculating duration time.
In this PR, I use the exist `Started` and `Stopped` column to record the
last run time instead of the total time,
and add a new `PreviousDuration` column to record the previous duration
time.
You can also check the cost time of last run:

![image](https://github.com/go-gitea/gitea/assets/18380374/2ca39145-2c92-401a-b78b-43164f7ae061)

models/migrations/migrations.go

@@ -554,6 +554,8 @@ var migrations = []Migration{
 	NewMigration("Add combined Index to issue_user.uid and issue_id", v1_22.AddCombinedIndexToIssueUser),
 	// v284 -> v285
 	NewMigration("Add ignore stale approval column on branch table", v1_22.AddIgnoreStaleApprovalsColumnToProtectedBranchTable),
+	// v285 -> v286
+	NewMigration("Add PreviousDuration to ActionRun", v1_22.AddPreviousDurationToActionRun),
 }
 
 // GetCurrentDBVersion returns the current db version