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/assignees.go

@@ -42,7 +42,7 @@ func (issue *Issue) LoadAssignees(ctx context.Context) (err error) {
 	if len(issue.Assignees) > 0 {
 		issue.Assignee = issue.Assignees[0]
 	}
-	return
+	return err
 }
 
 // GetAssigneeIDsByIssue returns the IDs of users assigned to an issue
@@ -167,5 +167,5 @@ func MakeIDsFromAPIAssigneesToAdd(oneAssignee string, multipleAssignees []string
 	// Get the IDs of all assignees
 	assigneeIDs, err = user_model.GetUserIDsByNames(requestAssignees, false)
 
-	return
+	return assigneeIDs, err
 }