Adds notifier_build lint (#2839) #4449

Job	Run time
build (stable, examples/counter)	1m 10s
build (stable, examples/marvel)	1m 25s
build (stable, examples/pub)	1m 33s
build (stable, examples/random_number)	1m 18s
build (stable, examples/stackoverflow)	1m 5s
build (stable, examples/todos)	1m 12s
build (stable, packages/riverpod)	3m 16s
build (stable, packages/riverpod/example)	1m 6s
build (stable, packages/flutter_riverpod)	1m 47s
build (stable, packages/flutter_riverpod/example)	1m 12s
build (stable, packages/hooks_riverpod)	1m 22s
build (stable, packages/hooks_riverpod/example)	1m 8s
build (stable, packages/riverpod_annotation)	51s
build (stable, packages/riverpod_generator)	2m 20s
build (stable, packages/riverpod_generator/integration/build_yaml)	2m 18s
build (stable, website)	1m 3s
build (master, examples/counter)	2m 16s
build (master, examples/marvel)	1m 29s
build (master, examples/pub)	1m 30s
build (master, examples/random_number)	1m 30s
build (master, examples/stackoverflow)	2m 9s
build (master, examples/todos)	1m 34s
build (master, packages/riverpod)	3m 33s
build (master, packages/riverpod/example)	1m 21s
build (master, packages/flutter_riverpod)	2m 20s
build (master, packages/flutter_riverpod/example)	1m 43s
build (master, packages/hooks_riverpod)	1m 35s
build (master, packages/hooks_riverpod/example)	1m 27s
build (master, packages/riverpod_annotation)	1m 24s
build (master, packages/riverpod_generator)	2m 22s
build (master, packages/riverpod_generator/integration/build_yaml)	2m 10s
build (master, website)	1m 35s
	54m 4s

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