Fix various issues with loading os definitions (#11640)

* Ping only device doesn't display
if os was set to something, ping os wasn't loaded and we try to get overview graphs from it.

* Fix snmp_disable device page load error
When other os is set.

* Revamp os setting loading
the only safe way to access is Config::getOsSetting()

* Remove getOsSetting fallback behavior
Most instances don't use it and it can have unexpected results Config::getOsSetting('blah', 'group') == 'librenms'

* refactor and remove unneeded load_os/loadOs calls now since getOsSetting automatically loads it.

* restore unix overview graphs, they are different
small cleanups

* fix

tests/OSDiscoveryTest.php

@@ -27,6 +27,9 @@ namespace LibreNMS\Tests;
 
 use Illuminate\Support\Str;
 use LibreNMS\Config;
+use LibreNMS\Util\OS;
+use const false;
+use const true;
 
 class OSDiscoveryTest extends TestCase
 {
@@ -145,7 +148,7 @@ class OSDiscoveryTest extends TestCase
         // make sure all OS are loaded
         $config_os = array_keys(Config::get('os'));
         if (count($config_os) < count(glob(Config::get('install_dir').'/includes/definitions/*.yaml'))) {
-            load_all_os();
+            OS::loadAllDefinitions(false, true);
             $config_os = array_keys(Config::get('os'));
         }