feat(spin): conditionally load runtime config from root #383

Job	Run time
rustfmt	19m 2s
build / build (ubuntu-latest, x86_64, slight, v1)	19m 5s
build-wasm-images / build_and_push (examples/spin-rust-hello, images/spin)	1m 51s
build / build (ubuntu-latest, x86_64, spin, v2)	19m 32s
build-wasm-images / build_and_push (examples/spin-dotnet-hello, images/spin_dotnet)	1m 21s
build / build (ubuntu-latest, x86_64, wws, v1)	30m 17s
build-wasm-images / build_and_push (examples/slight-rust-hello, images/slight)	5m 52s
build / build (ubuntu-latest, x86_64, lunatic, v1)	12m 50s
build-wasm-images / build_and_push (examples/wws-js-hello, images/wws)	22s
build / build (ubuntu-latest, aarch64, slight, v1)	19m 43s
build-wasm-images / build_and_push (examples/spin-inbound-redis, images/spin-inbound-redis)	56s
build / build (ubuntu-latest, aarch64, spin, v2)	36m 54s
build-wasm-images / build_and_push (examples/spin-outbound-redis, images/spin-outbound-redis)	1m 26s
build / build (ubuntu-latest, aarch64, wws, v1)	15m 56s
build-wasm-images / build_and_push (examples/lunatic-rust-hello, images/lunatic)	48s
build / build (ubuntu-latest, aarch64, lunatic, v1)	28m 1s
build-wasm-images / build_and_push (examples/lunatic-spawn, images/lunatic-spawn)	6m 17s
build-wasm-images / build_and_push (examples/lunatic-submillisecond, images/lunatic-submillisecond)	4m 10s
test	17m 28s
	4h 1m 51s

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