Added isEye and isZero to the Linear Algebra module.

[Iainmon]

Relevant issue:
#22682
It was pointed out that we should have isZero and isEye methods in the Linear Algebra module. This PR adds these.
Added two isEye and isZero to the linear algebra module.

• Paratest

[jeremiah-corrado]

This looks good overall, I just have a few questions:

[jeremiah-corrado]

Why do you have a separate implementation and public proc?

[Iainmon]

I was following the implicit convention that I saw. Such as

/* Return `true` if matrix is diagonal. */
proc isDiag(A: [?D] ?eltType) where isDenseMatrix(A) {
  return _isDiag(A);
}

private proc _isDiag(A: [?D] ?eltType) {
  if D.rank != 2 then
    compilerError("Rank is not 2");

  // Check if any element not along the diagonal is nonzero
  for (i, j) in D {
    if i != j && A[i, j] != 0 then return false;
  }
  return true;
}

where _isDiag is used in two different functions, one for dense matrices and one for sparse matrices.

[jeremiah-corrado]

Okay, that makes sense. I suspect other procs do it this way so that sparse and dense versions can use the same underlying implementation. I'd keep it this way.