[WIP] Implement CFI

[mohanson]

Implement CFI in the interpreter

$ cargo run --example ckb_vm_runner -- --mode interpreter64 ANY_PROGRAM_ENABLES_CFI

Implement a CFI Flags detector

$ cargo run --example cfi_detector --  ANY_PROGRAM_ENABLES_CFI
CFI_LP_UNLABELED: false
CFI_SS:           true
CFI_LP_FUNC_SIG:  false