feat: Define MSRV #7

Job	Run time
Dart test with Valgrind	4m 16s
Dart test with vm service	3m 1s
Flutter integration test on Android (pixel, 29)	8m 24s
Flutter integration test on Android (Nexus 6, 29)	8m 30s
Dart test on Web	8m 26s
Dart test on Web (wasm-start)	5m 48s
Flutter integration test on iOS (iPad (9th generation) Simulator (16.2))	8m 54s
Flutter integration test on iOS (iPhone 12 Pro Max Simulator (16.2))	6m 28s
Flutter integration test on Linux	5m 27s
Flutter integration test on MacOS	4m 9s
Rust build and test (macos-11)	1s
Rust build and test (windows-2019)	8m 29s
Rust build and test (ubuntu-latest)	6m 49s
Flutter integration test on Windows	8m 25s
Codegen (macos-11)	1s
Codegen (windows-2019)	7m 36s
Codegen (ubuntu-20.04)	4m 22s
Dart linter	1m 32s
test MSRV and specific problematic versions (nightly)	5m 7s
test MSRV and specific problematic versions (nightly-2023-06-28)	6m 57s
test MSRV and specific problematic versions (nightly-2023-07-26)	6m 58s
test MSRV and specific problematic versions (nightly-2022-07-15)	6m 27s
test MSRV and specific problematic versions (1.64)	6m 55s
Rust linter (1.68.0)	3m 40s
	2h 16m 42s

Provide feedback