Add conditional compilation for field sizes

[kevaundray]

Problem

Some functions require different parameters depending on the field being used. An example of this is poseidon, or the embedded curve that one can use.

Solution

One way to allow for this is to have a #[(field = "bls12381")] and or a #[(field = {primeNumber})] attribute which allows functions/modules to be conditionally compiled depending on the field being used.

Alternatives considered

One could manually namespace the function names, ie foo_bn254, foo_bls12_381 and change the code being called depending on whether the field changes

Additional context

(If applicable.)