feat: Define MSRV #15

Job	Run time
Dart test with Valgrind	3m 27s
Flutter integration test on MacOS	1s
Flutter integration test on Android (pixel, 29)	8m 30s
Flutter integration test on Android (Nexus 6, 29)	1s
Flutter integration test on iOS (iPad (9th generation) Simulator (16.2))	1s
Flutter integration test on iOS (iPhone 12 Pro Max Simulator (16.2))	1s
Flutter integration test on Windows	8m 37s
Codegen (macos-11)	1s
Codegen (windows-2019)	8m 44s
Codegen (ubuntu-20.04)	4m 17s
Dart linter	1m 55s
Dart test with vm service	3m 7s
Dart test on Web	4m 48s
Dart test on Web (wasm-start)	4m 42s
Flutter integration test on Linux	4m 39s
test MSRV and specific problematic versions (nightly)	5m 33s
test MSRV and specific problematic versions (nightly-2023-06-28)	6m 24s
test MSRV and specific problematic versions (nightly-2023-07-26)	8m 43s
test MSRV and specific problematic versions (nightly-2022-07-15)	6m 49s
test MSRV and specific problematic versions (1.64)	6m 38s
Rust build and test (macos-11)	1s
Rust build and test (windows-2019)	8m 35s
Rust build and test (ubuntu-latest)	4m 41s
Rust linter (1.68.0)	4m 34s
	1h 44m 49s

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