llm-factor: migrate to `candle` #6656

Job	Run time
Build Spin Ubuntu	20m 5s
Build Spin static (aarch64, aarch64-unknown-linux-musl)	16m 29s
all-integration-tests	23m 1s
Build Spin (windows-latest)	26m 11s
Build Spin static (amd64, x86_64-unknown-linux-musl)	14m 49s
Build Spin (macos-13)	23m 24s
Review new dependencies for known vulnerabilities	13s
Build Spin (macos-14)	10m 55s
Run release build steps (ubuntu-20.04, amd64, --features openssl/vendored, target/release)	15m 1s
Lint Rust	5m 47s
Run release build steps (ubuntu-20.04, aarch64, --features openssl/vendored --target aarch64-unkn...	15m 55s
Test Spin (ubuntu-22.04-4core-spin)	8m 9s
Run release build steps (macos-13, amd64, target/release)	27m 49s
Test Spin (macos-14)	25m 12s
Run release build steps (macos-14, aarch64, target/release)	13m 1s
Run release build steps (windows-latest, amd64, .exe, target/release)	27m 42s
	4h 33m 43s

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