Update winit_runner to use spawn_app for wasm32 target #53465

Job	Run time
build (windows-latest)	5m 45s
check-missing-examples-in-docs	33s
build (ubuntu-latest)	2m 41s
check-doc	7m 25s
check-bevy-internal-imports	4s
build (macos-latest)	2m 14s
ci	2m 55s
miri	12m 37s
run-examples-macos-metal	4m 52s
toml	1m 57s
typos	9s
check-missing-features-in-docs	28s
markdownlint	1m 43s
check-compiles	5m 16s
check-compiles-no-std	33s
build-wasm-atomics	1m 33s
msrv	1m 7s
build-wasm	57s
	52m 49s

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