Closes #134, #135

• Builtins initialization: in proof mode, all builtins of the layout are initialized but only the ones used by the program are appended to the stack.

• Specific stack initialization:

  • The Cairo Zero compiler adds instructions when compiling to proof mode, which requires prepending to the stack the the start of the builtin stack
  • The Cairo compiler does not add specific instructions, the end segment must be populated with a JumpRel 0 instruction.

• Introduces a RunnerMode enum for different initialization steps depending on the run context.

• The different checks (builtins usage, range_check, memory and diluted pool) have been inline in a single method checkCellsUsage(), which returns a boolean whether they passed for the chosen layout.