Add feature to support custom `now_utc` implementations #5026

Job	Run time
check-for-run-condition	1s
check-for-modification	4s
build-wasm / build-wasm (ubuntu-latest)	3m 8s
build-and-test (ubuntu-latest)	6m 9s
build-and-test (macos-latest)	3m 50s
build-and-test (windows-latest)	12m 23s
test-wasm (ubuntu-latest)	2m 29s
test-wasm-chrome (ubuntu-latest)	4m 17s
test-wasm-firefox (ubuntu-latest)	2m 55s
	35m 16s

Provide feedback