Feature: Proof mode for the VM

[rodrigo-pino]

To prove correct execution, the cairo-runner must show to the verifier the execution proof. This proof consists of two elements: the execution trace (PC_i, AP_i, FP_i) for each instruction and the resulting memory. To accomplish this we added:

1. Trace gathering while running instructions if PROOF_MODE is on.
2. Relocation logic to organize segments as continuos memory.
3. A new method Proof() which returns this values

[ElijahVlasov]

Great job! Some parts are thought-provoking so left some comments :)