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>

cmd/dummy-data-generator_test.go

@@ -61,7 +61,7 @@ func NewDummyDataGen(totalLength, skipOffset int64) io.ReadSeeker {
 		panic("Negative rotations are not allowed")
 	}
 
-	skipOffset = skipOffset % int64(len(alphabets))
+	skipOffset %= int64(len(alphabets))
 	as := make([]byte, 2*len(alphabets))
 	copy(as, alphabets)
 	copy(as[len(alphabets):], alphabets)