feat: Define MSRV #12

Job	Run time
Dart test with Valgrind	3m 29s
Flutter integration test on Windows	8m 20s
Flutter integration test on Android (pixel, 29)	8m 17s
Flutter integration test on Android (Nexus 6, 29)	8m 19s
Flutter integration test on iOS (iPad (9th generation) Simulator (16.2))	8m 39s
Flutter integration test on iOS (iPhone 12 Pro Max Simulator (16.2))	8m 24s
Codegen (macos-11)	5m 57s
Codegen (windows-2019)	8m 26s
Codegen (ubuntu-20.04)	3m 50s
Dart linter	1m 33s
Dart test with vm service	3m 36s
Dart test on Web	4m 6s
Dart test on Web (wasm-start)	4m 28s
Flutter integration test on Linux	4m 19s
Rust build and test (macos-11)	1s
Rust build and test (windows-2019)	7m 58s
Rust build and test (ubuntu-latest)	4m 57s
test MSRV and specific problematic versions (nightly)	6m 43s
test MSRV and specific problematic versions (nightly-2023-06-28)	6m 18s
test MSRV and specific problematic versions (nightly-2023-07-26)	6m 41s
test MSRV and specific problematic versions (nightly-2022-07-15)	8m 11s
test MSRV and specific problematic versions (1.64)	8m 9s
Rust linter (1.68.0)	4m 46s
Flutter integration test on MacOS	2m 13s
	2h 17m 40s

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