Add more linters to improve code readability (#19989)

Add nakedret, unconvert, wastedassign, stylecheck and nolintlint linters to improve code readability

- nakedret - https://github.com/alexkohler/nakedret - nakedret is a Go static analysis tool to find naked returns in functions greater than a specified function length.
- unconvert - https://github.com/mdempsky/unconvert - Remove unnecessary type conversions
- wastedassign - https://github.com/sanposhiho/wastedassign -  wastedassign finds wasted assignment statements.
- notlintlint -  Reports ill-formed or insufficient nolint directives
- stylecheck - https://staticcheck.io/docs/checks/#ST - keep style consistent
  - excluded: [ST1003 - Poorly chosen identifier](https://staticcheck.io/docs/checks/#ST1003) and [ST1005 - Incorrectly formatted error string](https://staticcheck.io/docs/checks/#ST1005)

models/issues/stopwatch.go

@@ -63,7 +63,7 @@ func getStopwatch(ctx context.Context, userID, issueID int64) (sw *Stopwatch, ex
 		Where("user_id = ?", userID).
 		And("issue_id = ?", issueID).
 		Get(sw)
-	return
+	return sw, exists, err
 }
 
 // UserIDCount is a simple coalition of UserID and Count
@@ -130,7 +130,7 @@ func HasUserStopwatch(ctx context.Context, userID int64) (exists bool, sw *Stopw
 	exists, err = db.GetEngine(ctx).
 		Where("user_id = ?", userID).
 		Get(sw)
-	return
+	return exists, sw, err
 }
 
 // FinishIssueStopwatchIfPossible if stopwatch exist then finish it otherwise ignore