Extract UI nodes into a Vec #56918

Job	Run time
ci	2m 56s
build (windows-latest)	13m 17s
miri	11m 27s
toml	2m 4s
build (ubuntu-latest)	8m 7s
build (macos-latest)	7m 25s
check-bevy-internal-imports	6s
check-doc	10m 32s
check-missing-examples-in-docs	30s
run-examples-macos-metal	5m 35s
typos	7s
check-missing-features-in-docs	33s
markdownlint	1m 11s
check-compiles-no-std	0s
check-compiles	0s
build-wasm-atomics	1m 43s
msrv	1m 23s
build-wasm	1m 28s
	1h 8m 24s

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