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/fs-v1.go

@@ -398,7 +398,7 @@ func (fs *FSObjects) scanBucket(ctx context.Context, bucket string, cache dataUs
 	return cache, err
 }
 
-/// Bucket operations
+// Bucket operations
 
 // getBucketDir - will convert incoming bucket names to
 // corresponding valid bucket names on the backend in a platform
@@ -601,7 +601,7 @@ func (fs *FSObjects) DeleteBucket(ctx context.Context, bucket string, opts Delet
 	return nil
 }
 
-/// Object Operations
+// Object Operations
 
 // CopyObject - copy object source object to destination object.
 // if source object and destination object are same we only