fix: Fix missing `OnEvent` callbacks with `IrisMethodChannel` used by multiple packages #167

Job	Run time
Build macOS (2.10.5)	4m 9s
Build iOS (2.10.5)	4m 15s
Build Android on Windows (2.10.5)	10m 12s
Build macOS (3.x)	3m 31s
Build Android on Ubuntu (2.10.5)	3m 39s
Build iOS (3.x)	3m 11s
Build Android on Windows (3.x)	7m 44s
Build Android on Ubuntu (3.x)	4m 17s
Build Web on Ubuntu (2.10.5)	1m 57s
pub.dev scores check	1m 40s
Build Windows (2.10.5)	6m 20s
Flutter code style check	1m 2s
Build Windows (3.x)	3m 48s
Build Web on Ubuntu (3.x)	1m 32s
android integration test	12m 41s
ios integration test	8m 54s
ios integration test with use_frameworks	11m 38s
macos integration test	4m 17s
windows integration test	5m 4s
pub publish check	1m 7s
Run flutter unit test (2.10.5)	1m 35s
Run flutter unit test web (2.10.5)	1m 39s
Run flutter unit test (3.x)	1m 22s
Run flutter unit test web (3.x)	1m 19s
	1h 46m 53s

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