[Sierra-Emu] Coverage tracking issue

[FrancoGiachetta]

We should increase the coverage of sierra-emu. Before doing so, we need to implement the todos left around the project:

• src/debug.rs
• src/main.rs
• src/value.rs
• src/vm/array.rs
• src/vm/bounded_int.rs
• src/vm/cast.rs
• src/vm/circuit.rs
• src/vm/const.rs
• src/vm/ec.rs
• src/vm/felt252.rs
• src/vm/gas.rs
• src/vm/int128.rs
• src/vm/starknet.rs
• src/vm/nullable.rs
• src/vm/uint8.rs
• src/vm/uint16.rs
• src/vm/uint32.rs
• src/vm/uint64.rs
• src/vm.rs

[FrancoGiachetta]

Finished with #1188