Refactor: combine Program.hints and Program.hints_ranges into a custom collection

[MegaRedHand]

Currently, the Program struct contains two fields hints and hints_ranges, where the second one is used to index the first.

cairo-vm/vm/src/types/program.rs

Lines 51 to 53 in 7e5378a

	pub(crate) hints: Vec<HintParams>,
	/// This maps a PC to the range of hints in `hints` that correspond to it.
	pub(crate) hints_ranges: Vec<HintRange>,

As they are strongly related two each other, they should be combined into a single collection that encapsulates the creation and indexing of hints. Some related functionality would be:

• Program::flatten_hints (a kind of constructor for it),

cairo-vm/vm/src/types/program.rs

Lines 121 to 124 in 7e5378a

	pub(crate) fn flatten_hints(
	hints: &HashMap<usize, Vec<HintParams>>,
	program_length: usize,
	) -> Result<(Vec<HintParams>, Vec<HintRange>), ProgramError> {

• and indexing operations (they are used in more than one place)

cairo-vm/vm/src/vm/runners/cairo_runner.rs

Lines 589 to 595 in 7e5378a

	let hint_data = self
	.program
	.shared_program_data
	.hints_ranges
	.get(vm.run_context.pc.offset)
	.and_then(|r| r.and_then(|(s, l)| hint_data.get(s..s + l.get())))
	.unwrap_or(&[]);

[PanGan21]

Hi! I did some effort to achieve this refactor in the pr mentioned above. Let me know if it would require more changes :)