Implements post-process film grain effects #73990

Job	Run time
check-doc	2m 9s
build (macos-latest)	2m 14s
miri	2m 12s
typos	10s
check-release-content	35s
ci	2m 9s
check-missing-examples-in-docs	35s
check-bevy-internal-imports	7s
toml	6s
build (ubuntu-latest)	2m 9s
build (windows-latest)	1m 59s
check-missing-features-in-docs	41s
markdownlint	1m 31s
check-compiles-no-std-portable-atomic	1s
check-compiles	1s
check-compiles-no-std	1s
check-compiles-no-std-examples	1s
msrv	1s
build-wasm	1s
build-wasm-atomics	1s
	16m 44s

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