Control when PHP's garbage collector is triggered

[sebastianbergmann]

When the PHP runtime automatically performs garbage collection then this may happen in the middle of the preparation (fixture setup) of a test or in the middle of the execution of a test. This can have a negative impact on test execution performance.

Solution proposed by @edorian in a conversation yesterday:

• Deactivate automatic garbage collection using gc_disable() before the first test is run
• Trigger garbage collection using gc_collect_cycles() before the first test is run
• Trigger garbage collection using gc_collect_cycles() after each n-th test
• Trigger garbage collection after using gc_collect_cycles() after the last test was run
• Activate automatic garbage collection using gc_enable() after the last test was run

• Implement GarbageCollectionHandler that implements the above using PHPUnit's event system
• Implement XML configuration file settings to configure this functionality
• Register GarbageCollectionHandler when feature is enabled in XML configuration

[codecov]

Codecov Report

Merging #5368 (6b73f0e) into main (0abe06b) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##               main    #5368      +/-   ##
============================================
+ Coverage     86.67%   86.73%   +0.06%     
- Complexity     6170     6198      +28     
============================================
  Files           652      660       +8     
  Lines         19635    19727      +92     
============================================
+ Hits          17019    17111      +92     
  Misses         2616     2616              

Impacted Files	Coverage Δ
src/Event/Emitter/DispatchingEmitter.php	95.94% <100.00%> (+0.08%)	⬆️
...nt/Events/TestRunner/GarbageCollectionDisabled.php	100.00% <100.00%> (ø)
...ent/Events/TestRunner/GarbageCollectionEnabled.php	100.00% <100.00%> (ø)
...t/Events/TestRunner/GarbageCollectionTriggered.php	100.00% <100.00%> (ø)
src/Event/Facade.php	89.04% <100.00%> (+0.22%)	⬆️
...ner/GarbageCollection/GarbageCollectionHandler.php	100.00% <100.00%> (ø)
...lection/Subscriber/ExecutionFinishedSubscriber.php	100.00% <100.00%> (ø)
...llection/Subscriber/ExecutionStartedSubscriber.php	100.00% <100.00%> (ø)
...Runner/GarbageCollection/Subscriber/Subscriber.php	100.00% <100.00%> (ø)
...geCollection/Subscriber/TestFinishedSubscriber.php	100.00% <100.00%> (ø)
... and 6 more

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