[TASK] Enable PHPUnit garbage collector control

[DanielSiepmann]

This is disabled by default and enabled with this change. This has the following effect:

• 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

Resolves: #1328

[coveralls]

Pull Request Test Coverage Report for Build 10148526231

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 10148327866:	0.0%
Covered Lines:	46
Relevant Lines:	46

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💛 - Coveralls