feat(realtime): add heartbeat callback #992

Job	Run time
Linux and Android	5m 55s
Examples	1m 47s
xcodebuild (16) (test, IOS, 16.3)	4m 1s
xcodebuild (15) (test, IOS, 15.4)	3m 6s
xcodebuild (16) (test, MACOS, 16.3)	2m 33s
xcodebuild (15) (test, MAC_CATALYST, 15.4)	1m 31s
xcodebuild (16) (IOS, 16.3)	2m 59s
xcodebuild (15) (test, MACOS, 15.4)	1m 23s
xcodebuild (16) (MACOS, 16.3)	2m 18s
xcodebuild (15) (test, TVOS, 15.4)	1m 55s
xcodebuild (15) (test, VISIONOS, 15.4)	3m 25s
xcodebuild (15) (IOS, 15.2)	1m 56s
xcodebuild (15) (IOS, 15.4)	1m 40s
xcodebuild (15) (MAC_CATALYST, 15.4)	1m 23s
xcodebuild (15) (MACOS, 15.2)	1m 39s
xcodebuild (15) (MACOS, 15.4)	1m 24s
xcodebuild (15) (TVOS, 15.4)	2m 18s
xcodebuild (15) (VISIONOS, 15.4)	1m 36s
xcodebuild (15) (WATCHOS, 15.4)	1m 47s
	44m 36s

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