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)

integrations/editor_test.go

@@ -82,7 +82,7 @@ func TestCreateFileOnProtectedBranch(t *testing.T) {
 			"_csrf":     csrf,
 			"protected": "off",
 		})
-		resp = session.MakeRequest(t, req, http.StatusSeeOther)
+		session.MakeRequest(t, req, http.StatusSeeOther)
 		// Check if master branch has been locked successfully
 		flashCookie = session.GetCookie("macaron_flash")
 		assert.NotNil(t, flashCookie)
@@ -109,7 +109,7 @@ func testEditFile(t *testing.T, session *TestSession, user, repo, branch, filePa
 			"commit_choice": "direct",
 		},
 	)
-	resp = session.MakeRequest(t, req, http.StatusSeeOther)
+	session.MakeRequest(t, req, http.StatusSeeOther)
 
 	// Verify the change
 	req = NewRequest(t, "GET", path.Join(user, repo, "raw/branch", branch, filePath))
@@ -139,7 +139,7 @@ func testEditFileToNewBranch(t *testing.T, session *TestSession, user, repo, bra
 			"new_branch_name": targetBranch,
 		},
 	)
-	resp = session.MakeRequest(t, req, http.StatusSeeOther)
+	session.MakeRequest(t, req, http.StatusSeeOther)
 
 	// Verify the change
 	req = NewRequest(t, "GET", path.Join(user, repo, "raw/branch", targetBranch, filePath))