Implement equality comparisons on System.Array

[BCSharp]

Fixes IndexOutOfRangeException when equating arrays with different index bases (lower bounds).

Example:

>>> from System import *
>>> a = Array.CreateInstance(Int32, (5,), (1,))
>>> b = Array.CreateInstance(Int32, (5,), (1,))
>>> a == b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: Index was outside the bounds of the array.
>>> a != b
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: Index was outside the bounds of the array.

This is due to a bug in .NET:

var a = Array.CreateInstance(typeof(int), new[] { 5 }, new[] { 1 });
var b = Array.CreateInstance(typeof(int), new[] { 5 }, new[] { 1 });
((IStructuralEquatable)a).Equals(b, EqualityComparer<int>.Default);  // IndexOutOfRangeException

I'll see if this is already reported. It just shows that nonzero bases are not very popular.

In this PR I'll also cover equating multidimensional arrays, since there is just a little bit to add to address that as well.

[BCSharp]

Ordering comparisons are also not working well, but I leave it as that — I don't have old code to submit.

[slozier]

Thanks, seems fine to me. I'll file an issue regarding array ordering comparisons not working since this seems to be a regression from 2.7.