Update hashbrown to 0.15 #50997

Job	Run time
check-bevy-internal-imports	5s
check-missing-examples-in-docs	30s
build (windows-latest)	10m 23s
check-doc	5m 3s
build (ubuntu-latest)	4m 31s
ci	4m 50s
build (macos-latest)	3m 30s
miri	10m 39s
run-examples-macos-metal	6m 5s
toml	2m 8s
typos	7s
check-missing-features-in-docs	32s
markdownlint	1m 5s
check-compiles	6m 41s
check-compiles-no-std	30s
msrv	1m 53s
build-wasm-atomics	1m 54s
build-wasm	1m 44s
	1h 2m 10s

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