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/web/repo/editor_test.go

@@ -70,9 +70,7 @@ func TestGetClosestParentWithFiles(t *testing.T) {
 	gitRepo, _ := git.OpenRepository(git.DefaultContext, repo.RepoPath())
 	defer gitRepo.Close()
 	commit, _ := gitRepo.GetBranchCommit(branch)
-	expectedTreePath := ""
-
-	expectedTreePath = "" // Should return the root dir, empty string, since there are no subdirs in this repo
+	var expectedTreePath string // Should return the root dir, empty string, since there are no subdirs in this repo
 	for _, deletedFile := range []string{
 		"dir1/dir2/dir3/file.txt",
 		"file.txt",