[BUGFIX] Don’t do greedy merges in extension scanner

The extension scanner merges all matches into an array. This is done in a
loop, which is pretty greedy as it impacts CPU and RAM.

Instead, it's possible to do a single array_merge() at the end of the
loop.

See this document for reference:
https://github.com/kalessil/phpinspectionsea/blob/master/docs/performance.md#slow-array-function-used-in-loop

Resolves: #86282
Releases: master
Change-Id: I09b45468dfd9f60ce6bd9e264ecfc3cbfcb54fa1
Reviewed-on: https://review.typo3.org/58302


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>