add gocritic/ruleguard checks back again, cleanup code. (#13665)

- remove some duplicated code
- reported a bug, separately fixed in #13664
- using strings.ReplaceAll() when needed
- using filepath.ToSlash() use when needed
- remove all non-Go style comments from the codebase

Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>

internal/s3select/simdj/reader_amd64_test.go

@@ -87,7 +87,7 @@ func TestNDJSON(t *testing.T) {
 			if false {
 				t.Log(string(b))
 			}
-			//_ = ioutil.WriteFile(filepath.Join("testdata", tt.name+".json"), b, os.ModePerm)
+			// _ = ioutil.WriteFile(filepath.Join("testdata", tt.name+".json"), b, os.ModePerm)
 
 		parser:
 			for {