Ensure error handling in CoreGraphics and attendant frameworks happens at API boundaries

[DHowett-MSFT]

• All internal methods should be able to report failure without aborting, whether through an HRESULT return or a nullptr return.
• All external API surface methods should be able to fail where possible.
  • Some frameworks do not provide for errors to be returned. The reference platform has been observed calling abort().
  • If there is an opportunity for a failure return, it should be taken. API functions that can return newly-created resources are safe to return nothing and emit a trace error.

[rajsesh]

We have normalized the design on this, so we can close this now.