Improve SnmpResponse value() (#14605)

* Improve SnmpResponse value
Can now return a specific oid or the first non-empty oid in a list.
Cache values() call on object to avoid repeated parsing
Improved types

* fix style

* extract getOidParts to fix errors from different parts of the code parsing differently

* new object to deal with cache

* More tests

* whitespace

* style

LibreNMS/Modules/Core.php

@@ -236,7 +236,7 @@ class Core implements Module
                     ->options($value['options'] ?? null)
                     ->mibDir($value['mib_dir'] ?? $mibdir)
                     ->walk(isset($value['mib']) ? "{$value['mib']}::{$value['oid']}" : $value['oid'])
-                    ->raw();
+                    ->raw;
                 if (Compare::values($walk_value, $value['value'], $value['op'] ?? 'contains') == $check) {
                     return false;
                 }