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/sql/value.go

@@ -231,6 +231,7 @@ func (v Value) ToArray() (val []Value, ok bool) {
 
 // IsNull - checks if value is missing.
 func (v Value) IsNull() bool {
+	//nolint:gocritic
 	switch v.value.(type) {
 	case nil:
 		return true
@@ -245,6 +246,7 @@ func (v Value) IsArray() (ok bool) {
 }
 
 func (v Value) isNumeric() bool {
+	//nolint:gocritic
 	switch v.value.(type) {
 	case int64, float64:
 		return true