adds final support for arrays, by supporting output and reference arrays.

These two implementations are fairly similar, so that's why i did them in one go. The only difference is that for output arrays the callee allocates the buffer (via CoTaskMemAlloc) and in reference arrays, the caller pre-allocates the buffer and it is filled in by the callee. Since Swift doesn't have true "out" params, the APIs for these on the Swift side are identical (both inout [T]) which could lead to some confusion. Possible improvement may be to use something like ArraySlice for reference arrays?

Changes

1. Update Array+ToABI.swift to support allocating+filling a WinRT buffer.
2. Updates Array+ToABI.swift to use the same WinRTArrayABI typealias that Array+FromAbi.swift uses. This made code-gen simpler
3. For non-blittable reference arrays, we have to copy the buffer back into the swift array.
4. Had to undef GetGlyphIndices as this conflicts with Win2D API (would love to not use any Windows headers!!)
5. Cleaned up can_write.h since we now can generate the full projection. It only exists to not include APIs which were filtered out.

Arc builds/runs with the needed changes to remove the handwritten APIs we created due to lack of array support in swift-winrt.