Support user metadata on activities and child/scheduled workflows #2286

Job	Run time
cloud-test	0s
build-and-test (ubuntu-latest, oldstable)	17m 8s
build-and-test (ubuntu-latest, stable)	25m 48s
build-and-test (macos-intel, oldstable)	4m 10s
build-and-test (macos-intel, stable)	18m 3s
build-and-test (macos-arm, oldstable)	17m 3s
build-and-test (macos-arm, stable)	16m 39s
build-and-test (windows-latest, oldstable)	21m 17s
build-and-test (windows-latest, stable)	20m 51s
features-test / test	2m 16s
	2h 23m 15s

Provide feedback