Improve CI (#31) #23

Job	Run time
Tests / Fetch supported versions	4s
Tests / Static analysis	22s
Tests / Up to date versions	2m 58s
Tests / Late migration - Symfony	2m 23s
Tests / Bare minimum	20s
Tests / Bare minimum - Special case - Symfony 5.4	18s
Tests / Late migration - PHP	20s
Tests / Up to date versions - Special case - Symfony 5.4	2m 56s
Tests / Nightly - PHP - With highest supported Symfony versions	18s
Tests / Nightly - Symfony - With highest supported PHP version	19s
Tests / Nightly - Symfony - With lowest supported PHP version	22s
Tests / Nightly - PHP - With lowest supported Symfony versions	14s
	10m 54s

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