llm-factor: migrate to `candle` #6654

Job	Run time
Lint Rust	9m 36s
Build Spin Ubuntu	22m 13s
all-integration-tests	25m 19s
Build Spin (windows-latest)	46m 32s
Build Spin static (aarch64, aarch64-unknown-linux-musl)	16m 25s
Review new dependencies for known vulnerabilities	16s
Build Spin (macos-13)	30m 46s
Build Spin static (amd64, x86_64-unknown-linux-musl)	16m 16s
Build Spin (macos-14)	18m 33s
Run release build steps (ubuntu-20.04, amd64, --features openssl/vendored, target/release)	15m 0s
Test Spin (ubuntu-22.04-4core-spin)	14m 41s
Run release build steps (ubuntu-20.04, aarch64, --features openssl/vendored --target aarch64-unkn...	16m 8s
Test Spin (macos-14)	28m 1s
Run release build steps (macos-13, amd64, target/release)	24m 16s
Run release build steps (macos-14, aarch64, target/release)	13m 27s
Run release build steps (windows-latest, amd64, .exe, target/release)	24m 57s
	5h 22m 26s

Provide feedback