reflect: implement the unique reflect rfc #39762

Job	Run time
ci	2m 24s
check-doc	7m 33s
check-missing-examples-in-docs	28s
build (windows-latest)	4m 25s
miri	6m 3s
build (ubuntu-latest)	2m 31s
run-examples-macos-metal	4m 18s
build (macos-latest)	8m 1s
toml	2m 9s
typos	5s
check-bevy-internal-imports	3s
check-cfg	1m 8s
check-missing-features-in-docs	29s
markdownlint	1m 11s
check-compiles	1m 24s
msrv	1m 11s
build-wasm-atomics	1m 20s
build-wasm	1m 1s
	45m 44s

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