llm-factor: migrate to `candle` #6696

Job	Run time
Build Spin static (aarch64, aarch64-unknown-linux-musl)	17m 35s
Build Spin (windows-latest)	44m 53s
all-integration-tests	23m 14s
Build Spin static (amd64, x86_64-unknown-linux-musl)	15m 59s
Build Spin Ubuntu	21m 33s
Build Spin (macos-13)	27m 3s
Build Spin (macos-14)	20m 59s
Review new dependencies for known vulnerabilities	13s
Lint Rust	10m 11s
Run release build steps (ubuntu-20.04, amd64, --features openssl/vendored, target/release)	15m 7s
Test Spin (ubuntu-22.04-4core-spin)	15m 30s
Run release build steps (ubuntu-20.04, aarch64, --features openssl/vendored --target aarch64-unkn...	15m 57s
Test Spin (macos-14)	29m 22s
Run release build steps (macos-13, amd64, target/release)	25m 51s
Run release build steps (macos-14, aarch64, target/release)	12m 58s
Run release build steps (windows-latest, amd64, .exe, target/release)	26m 5s
	5h 22m 30s

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