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/erasure-coding.go

@@ -95,7 +95,7 @@ func (e *Erasure) EncodeData(ctx context.Context, data []byte) ([][]byte, error)
 // It returns an error if the decoding failed.
 func (e *Erasure) DecodeDataBlocks(data [][]byte) error {
 	var isZero = 0
-	for _, b := range data[:] {
+	for _, b := range data {
 		if len(b) == 0 {
 			isZero++
 			break