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/endpoint.go

@@ -497,6 +497,7 @@ func NewEndpoints(args ...string) (endpoints Endpoints, err error) {
 		}
 
 		// All endpoints have to be same type and scheme if applicable.
+		//nolint:gocritic
 		if i == 0 {
 			endpointType = endpoint.Type()
 			scheme = endpoint.Scheme