Remove std::merkle::check_membership

[TomAFrench]

Problem

The stdlib function check_membership is pretty trivial and is less readable than performing the equality check in user code imo.

noir/noir_stdlib/src/merkle.nr

Lines 3 to 10 in a830ce5

	// Returns one if the leaf is in the tree
	// and it is at the given index
	// and the hashpath proves this
	// Currently we assume that it is a binary tree, so depth k implies a width of 2^k
	// XXX: In the future we can add an arity parameter
	fn check_membership(_root : Field, _leaf : Field, _index : Field, _hash_path: [Field]) -> Field {
	(compute_merkle_root(_leaf, _index, _hash_path) == _root) as Field
	}

Proposed solution

We should remove std::merkle::check_membership and push people towards using compute_merkle_root.

Alternatives considered

Alternatively we can retain this function but update the return type to bool

Additional context

Related to #1258

Submission Checklist

• Once I hit submit, I will assign this issue to the Project Board with the appropriate tags.

[TomAFrench]

Closed in #1424