Implement logic to run monitors and tasks

A few code sniffs fixes. Here is the gitlab branch compare,
https://git.drupalcode.org/project/system_monitor/compare/8.x-1.x...task...

What's going on here, why do we have to pass the class name as string?

SystemMonitorTaskManager::__construct()

public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler, EntityTypeManagerInterface $entity_type_manager, LoggerChannelFactoryInterface $logger, SystemMonitorUtility $system_monitor_utility) {
    parent::__construct(
      'Plugin/SystemMonitorTask',
      $namespaces,
      $module_handler,
      'Drupal\system_monitor\SystemMonitorTaskInterface',
      'Drupal\system_monitor\Annotation\SystemMonitorTask');
...
...

Nice work!

+      '#value' => $this->t('Select which tasks to run when this monitor is executed. <em>If nothing is selected then all tasks will be run.</em>'),

I don't think the em tag is necessary here.

// @TODO: Update options once Event logic is in place.

The correct docblock syntax is @todo without the colon.

+      $tasks = $this->systemMonitorUtility->getAvailableTasksByMonitorId($monitor);
+      if (!empty($tasks)) {
+        foreach ($tasks as $task) {

If getAvailableTasksByMonitorId() always returns an array you could skip the if(!empty()) and just go straight to foreach($this->systemMonitorUtility->getAvailableTasksByMonitorId($monitor)), though that is a little long for a single line. :shrug: :)

General notes:

• A few functions need parameter descriptions.

You should demo this at the next dev team meeting :-)