ci: pin cross and rust versions #419

Job	Run time
rustfmt	12m 8s
build / build (ubuntu-latest, x86_64, slight, v1)	18m 38s
build-wasm-images / build_and_push (examples/spin-rust-hello, images/spin)	1m 21s
build / build (ubuntu-latest, x86_64, spin, v2)	21m 58s
build-wasm-images / build_and_push (examples/spin-dotnet-hello, images/spin_dotnet)	1m 4s
build / build (ubuntu-latest, x86_64, wws, v1)	13m 56s
build-wasm-images / build_and_push (examples/slight-rust-hello, images/slight)	2m 38s
build / build (ubuntu-latest, x86_64, lunatic, v1)	13m 4s
build-wasm-images / build_and_push (examples/wws-js-hello, images/wws)	16s
build / build (ubuntu-latest, aarch64, slight, v1)	19m 42s
build-wasm-images / build_and_push (examples/spin-inbound-redis, images/spin-inbound-redis)	1m 5s
build / build (ubuntu-latest, aarch64, spin, v2)	22m 34s
build-wasm-images / build_and_push (examples/spin-outbound-redis, images/spin-outbound-redis)	58s
build / build (ubuntu-latest, aarch64, wws, v1)	14m 58s
build-wasm-images / build_and_push (examples/lunatic-rust-hello, images/lunatic)	28s
build / build (ubuntu-latest, aarch64, lunatic, v1)	13m 3s
build-wasm-images / build_and_push (examples/lunatic-spawn, images/lunatic-spawn)	2m 37s
build-wasm-images / build_and_push (examples/lunatic-submillisecond, images/lunatic-submillisecond)	2m 52s
test	11m 11s
	2h 54m 31s

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