Check license header in `flutter analyze` #2292

Job	Run time
test / test-dart-vm (3.9.0)	1m 35s
test / test-dart-vm (stable)	1m 41s
ddc_test / test-dart-ddc (3.9.0, chrome)	4m 13s
ddc_test / test-dart-ddc (3.9.0, firefox)	4m 16s
ddc_test / test-dart-ddc (stable, firefox)	4m 14s
ddc_test / test-dart-ddc (stable, chrome)	3m 56s
dart2js_test / test-dart-2js (stable, chrome)	6m 56s
native_test / test-dart-native (macos-14)	3m 15s
dart2js_test / test-dart-2js (stable, firefox)	7m 27s
dart2js_test / test-dart-2js (3.9.0, chrome)	7m 5s
native_test / test-dart-native (windows-latest)	3m 9s
dart2js_test / test-dart-2js (3.9.0, firefox)	7m 31s
	55m 18s

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