refactor: make limbs generic to accept limb size

[0xkanekiken]

This PR tries to make the Limbs to be generic in the number of limbs size so that it could support points from different curves. At the moment the LIMB_SIZE is hardcoded to 32.

sp1/core/src/operations/field/field_den.rs

Lines 21 to 29 in 809f5c4

	#[derive(Debug, Clone, AlignedBorrow)]
	#[repr(C)]
	pub struct FieldDenCols<T> {
	/// The result of `a den b`, where a, b are field elements
	pub result: Limbs<T>,
	pub(crate) carry: Limbs<T>,
	pub(crate) witness_low: [T; NUM_WITNESS_LIMBS],
	pub(crate) witness_high: [T; NUM_WITNESS_LIMBS],
	}

Major changes:

• The number of witnesses is determined by 2 * NUM_LIMBS - 2, which in the above example, can be set to 2 * N - 2 where N is the const generic passed to the struct. Unfortunately, passing a generic to a constant operation is not supported in stable Rust, and requires the use of the nightly version. To circumvent this, introduced an additional const parameter for the number of witnesses. Need to figure out the best way to handle this.
• Introduced a proc macroAlignedBorrowWithGenerics, to address the above issue. This implementation is not the cleanest and I am looking ways to modify AlignedBorrow to support use cases where the first generic is a type, and the rest are constants. At the very least, it should be capable of handling cases where the first generic is the type, and all subsequent generics are constants using one proc macro.
• currently- I have disabled weierstrass related mods to check if it works with the edwards curve. I plan to enable them subsequently.

[puma314]

I wonder if there's some way to get all the generics from the ast, similar to the name parameter.

[tamirhemo]

Generic can be obtained from the derive macro token stream:
https://docs.rs/syn/latest/syn/struct.DeriveInput.html

@0xkanekiken I think your implementation could be changed a bit to support reading generic constants. There are ways to read the generics and add a new one (like T). Would be happy to chat about it more.

[0xkanekiken]

Please see the commit diff. I've modified the AlignedBorrow macro to support constant generics.

[tamirhemo]

Could you also add a panic! that would occur if a non-const generic is used other than T? that would be really good for our user experience which might not be clear right now.

[0xkanekiken]

Please see #368. Infact, I have modified the code to trigger a panic if the first generic is not a type, and for any subsequent generics, if they are not consts.

[puma314]

Closing in favor of this approach: #417