Update deprecated actions/checkout; lint against PHP 8.4 #211

Job	Run time
Static Analysis	1m 31s
Lint (5.3, false)	19s
Lint (5.4, false)	16s
Lint (5.5, false)	16s
Lint (5.6, false)	14s
Lint (7.0, false)	9s
Lint (7.1, false)	12s
Lint (7.2, false)	15s
Lint (7.3, false)	16s
Lint (7.4, false)	10s
Lint (8.0, false)	9s
Lint (8.1, false)	1m 53s
Lint (8.2, false)	16s
Lint (8.3, false)	15s
Lint (8.4, true, --ignore-platform-reqs)	14s
	6m 25s

Provide feedback