[directxtk, directxtk12, directxtex] ports updated for August 2021 release#19320

Merged

BillyONeal merged 7 commits intomicrosoft:masterfrom

walbourn:aug2021update

Aug 26, 2021

Commits on Aug 8, 2021

Added 4.7.2 .NET TargetingPack
walbourn
committed

Commits on Aug 26, 2021

Back out adding .NET targeting pack, forked out as https://github.com/microsoft/vcpkg/pull/19764
BillyONeal
committed