Implement support for flat collections in `Mixed` #4042

Job	Run time
Build for linux x64	9m 49s
Bundle TypeScript	2m 59s
Build for linux arm	9m 4s
Build for linux arm64	9m 35s
Build for windows x64	11m 17s
Build for windows ia32	13m 15s
Build for android x86_64	6m 43s
Build for android armeabi-v7a	6m 35s
Build for android arm64-v8a	6m 42s
Build for android x86	6m 28s
Build for darwin x64	26m 11s
Build for darwin arm64	17m 11s
Build for ios simulator	19m 8s
Build for ios catalyst	6m 39s
Build for ios ios	6m 38s
Generate Info.plist with all frameworks in place	30s
Test node on linux (test:ci)	6m 6s
Test electron on linux (test:ci:main)	4m 56s
Test electron on linux (test:ci:renderer)	5m 21s
Test electron on darwin (test:ci:main)	6m 27s
Test electron on darwin (test:ci:renderer)	8m 29s
Test node on darwin (test:ci)	9m 14s
Test react-native on android (test:ci:android)	21m 49s
Test react-native on ios (test:ci:ios)	20m 21s
	4h 1m 27s

Provide feedback