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)

routers/api/v1/repo/file.go

@@ -251,7 +251,7 @@ func getBlobForEntry(ctx *context.APIContext) (blob *git.Blob, lastModified time
 	}
 	blob = entry.Blob()
 
-	return
+	return blob, lastModified
 }
 
 // GetArchive get archive of a repository

routers/api/v1/repo/issue_label.go

@@ -321,5 +321,5 @@ func prepareForReplaceOrAdd(ctx *context.APIContext, form api.IssueLabelsOption)
 		return
 	}
 
-	return
+	return issue, labels, err
 }

routers/api/v1/repo/status.go

@@ -57,7 +57,7 @@ func NewCommitStatus(ctx *context.APIContext) {
 		return
 	}
 	status := &git_model.CommitStatus{
-		State:       api.CommitStatusState(form.State),
+		State:       form.State,
 		TargetURL:   form.TargetURL,
 		Description: form.Description,
 		Context:     form.Context,