Add DanglingSpansShutdownHandler for cleaning up dangling spans / contexts #2357

Job	Run time
php (7.4, false)	1m 4s
php (8.0, false)	42s
php (8.1, false)	40s
php (8.2, false)	38s
php (8.3, false)	51s
php (8.4, true, --ignore-platform-reqs)	18m 46s
packages	0s
	22m 41s

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