Remaining work for windows targeting

[marcpopMSFT]

• Investigate benefits of using crossgen for CSWinRT assets. Investigate crossgen performance impact with CsWinRT generated SDK interop microsoft/CsWinRT#317 Depending on the results of this:
  • Create separate runtime packs for each architecture with crossgen'd versions of CSWinRT assets
  • Update .NET SDK to consume these runtime packs

[wli3]

#12456 is 5.0 work the rest is 6.0. Move this issue to 6.0 since #12456 tracked separately

[marcpopMSFT]

@angelazhangmsft is this still important for your scenario?