Use `EntityHashMap` for `EntityMapper` #31920

Job	Run time
build (windows-latest)	6m 35s
build (windows-latest)	6m 35s
build (windows-latest)	6m 35s
check-doc	7m 16s
check-doc	7m 16s
check-doc	7m 16s
check-bevy-internal-imports	3s
check-bevy-internal-imports	3s
check-bevy-internal-imports	3s
build (ubuntu-latest)	1m 42s
build (ubuntu-latest)	1m 42s
build (ubuntu-latest)	1m 42s
check-missing-examples-in-docs	42s
check-missing-examples-in-docs	42s
check-missing-examples-in-docs	42s
build (macos-latest)	2m 50s
build (macos-latest)	2m 50s
build (macos-latest)	2m 50s
ci	2m 16s
ci	2m 16s
ci	2m 16s
miri	6m 0s
miri	6m 0s
miri	6m 0s
run-examples-on-windows-dx12	15m 8s
run-examples-on-windows-dx12	15m 8s
run-examples-on-windows-dx12	15m 8s
check-missing-features-in-docs	1m 1s
check-missing-features-in-docs	1m 1s
check-missing-features-in-docs	1m 1s
markdownlint	1m 45s
markdownlint	1m 45s
markdownlint	1m 45s
check-compiles	3m 1s
check-compiles	3m 1s
check-compiles	3m 1s
msrv	52s
msrv	52s
msrv	52s
build-wasm	35s
build-wasm	37s
build-wasm	46s
	2h 29m 31s

Provide feedback