Lift http handler type discovery up a layer #5708

Job	Run time
Build Spin static (aarch64, aarch64-unknown-linux-musl)	14m 3s
Build Spin (windows-latest)	23m 17s
Build Spin static (amd64, x86_64-unknown-linux-musl)	13m 20s
Build Spin Ubuntu	18m 24s
Build Spin (macos-latest)	15m 48s
all-integration-tests	27m 0s
Lint Rust	5m 38s
Test Spin (ubuntu-22.04-4core-spin)	11m 6s
Run release build steps (ubuntu-20.04, amd64, --features openssl/vendored, target/release)	13m 46s
Run release build steps (ubuntu-20.04, aarch64, --features openssl/vendored --target aarch64-unkn...	14m 10s
Run release build steps (macos-latest, amd64, target/release)	22m 33s
Test Spin (macos-latest)	31m 29s
Run release build steps (macos-latest, aarch64, --target aarch64-apple-darwin, aarch64-apple-darw...	16m 12s
Run release build steps (windows-latest, amd64, .exe, target/release)	24m 19s
	4h 11m 5s

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