add DI container support

[LordSimal]

Fixes #324

This implementation allows the user to get access to the DI container instance via adding

public function services(ContainerInterface $container): void {
	$this->testService = $container->get(TestService::class);
}

to the desired task.

I first thought to implement the same behaviour as it is present in the controller where the services() method automatically detects the desired services via the argument types but i think it is easier to just pass the DI container instance to the task and the user can retrieve as many services as he wants from that instance.

The only thing I am not really sure if its the "correct" way is the fact how I inject the container instance into the processor (and therefore into the task) - see bellow my github code comment.

[codecov-commenter]

Codecov Report

Merging #327 (d75f57b) into master (d46358e) will decrease coverage by 0.17%.
The diff coverage is 35.29%.

@@             Coverage Diff              @@
##             master     #327      +/-   ##
============================================
- Coverage     57.74%   57.57%   -0.18%     
- Complexity      658      665       +7     
============================================
  Files            35       36       +1     
  Lines          2123     2138      +15     
============================================
+ Hits           1226     1231       +5     
- Misses          897      907      +10     

Impacted Files	Coverage Δ
src/Command/RunCommand.php	0.00% <0.00%> (ø)
src/Controller/Admin/QueueProcessesController.php	81.39% <ø> (ø)
src/Controller/Admin/QueuedJobsController.php	47.30% <ø> (ø)
src/Model/Table/QueueProcessesTable.php	81.89% <ø> (ø)
src/Model/Table/QueuedJobsTable.php	40.05% <ø> (ø)
src/Queue/ServicesTrait.php	0.00% <0.00%> (ø)
src/Queue/Processor.php	12.84% <40.00%> (+0.27%)	⬆️
src/Plugin.php	100.00% <100.00%> (ø)

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[dereuromark]

Sounds pretty BC safe to me now.

[LordSimal]

Should I ignore that phpcs error regarding Invalid Inline Doc Block? Or what exactly is wrong there?

[dereuromark]

Can you maybe add some docs for it too?
So people know how to use it?