[Feat]: Add an 'in' instruction in the VM.

[usagi32]

Motivation

for this issue in leo ProvableHQ/leo#28721

This PR adds a new 'in' instruction support at the synthesizer level. Without this developers would have to do a verbose unroll of the entire array and also instruction costs would increase for contracts for multiple checks, so this saves that.

Some notes:

• The tests currently only checks for single dimensional literal arrays as for multi dimensional arrays and struct struct arrays, it would require a slight different infrastructure then the rest of the tests. But also there's no reason implementation won't work for all kinds of arrays.
• Maybe the cost function can be optimized more, for e.g. rather than a constant, some heuristic approximation or maybe even linear multiple of the recursive array length, considering all the the inner members in structs etc.

If this PR is approved, I would also add the support in leo as well.

Test Plan

Added new tests

[d0cd]

I do not believe that this is sufficiently constrained. Generally, eject_value needs to be used with care in a circuit. One safe way to implement this is to construct an "or" expression over all of the equality operations, e.g, (val == arr[0] || val == arr[1] || ... || val == arr[k])

[usagi32]

done