Bump min sdk versions in DevTools packages. #11422

Job	Run time
flutter-prep / ubuntu-latest Flutter Prep	41s
flutter-prep / macos-latest Flutter Prep	1m 21s
Dart Code Metrics	5m 24s
devtools_extensions integration-test integration_dart2js	10m 10s
macos goldens test_dart2js	8m 2s
devtools_app integration-test integration_dart2js - flutter - shard 1/3	13m 21s
main	6m 0s
devtools_app integration-test integration_dart2js - flutter - shard 2/3	19m 53s
devtools_app integration-test integration_dart2js - flutter - shard 3/3	21m 23s
build_ddc	3m 18s
devtools_app integration-test integration_dart2js - flutter-web - shard 1/2	13m 42s
build_dart2js	3m 18s
devtools_app integration-test integration_dart2js - flutter-web - shard 2/2	19m 21s
test_ddc	7m 42s
devtools_app integration-test integration_dart2js - dart-cli - shard 1/1	15m 55s
test_dart2js	12m 45s
benchmarks_dart2js	5m 17s
	2h 47m 33s

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