ci: pin cross and rust versions #413

Job	Run time
rustfmt	12m 56s
build / build (ubuntu-latest, x86_64, slight, v1)	2m 0s
build / build (ubuntu-latest, x86_64, spin, v2)	2m 0s
build-wasm-images / build_and_push (examples/spin-rust-hello, images/spin)	1m 18s
build / build (ubuntu-latest, x86_64, wws, v1)	1m 59s
build-wasm-images / build_and_push (examples/spin-dotnet-hello, images/spin_dotnet)	1m 7s
build / build (ubuntu-latest, x86_64, lunatic, v1)	2m 1s
build-wasm-images / build_and_push (examples/slight-rust-hello, images/slight)	1m 17s
build / build (ubuntu-latest, aarch64, slight, v1)	1m 43s
build-wasm-images / build_and_push (examples/wws-js-hello, images/wws)	34s
build / build (ubuntu-latest, aarch64, spin, v2)	2m 0s
build-wasm-images / build_and_push (examples/spin-inbound-redis, images/spin-inbound-redis)	1m 12s
build / build (ubuntu-latest, aarch64, wws, v1)	2m 0s
build-wasm-images / build_and_push (examples/spin-outbound-redis, images/spin-outbound-redis)	56s
build / build (ubuntu-latest, aarch64, lunatic, v1)	1m 59s
build-wasm-images / build_and_push (examples/lunatic-rust-hello, images/lunatic)	52s
build-wasm-images / build_and_push (examples/lunatic-spawn, images/lunatic-spawn)	1m 16s
build-wasm-images / build_and_push (examples/lunatic-submillisecond, images/lunatic-submillisecond)	1m 19s
test	0s
	38m 29s

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