Security bug in ConvertToSinglePlane when used with untrusted content from the DDS loader
### Impact
A memory overwrite bug was reported by a security researcher in the **ConvertToSinglePlane** method via the *texconv* command-line tool when given an invalid height for planar video textures such as NV12. This can be a potential security bug for any clients of the library who follow the same pattern.
This issue *does not* impact use of the DDS texture loader itself, only when combined with `ConvertToSinglePlane` for converting multi-planar video formats. All other functions in the library fail immediately if given images in planar formats.
### Patches
The fix to the specific area as well as general hardening can be found in this PR
https://github.com/microsoft/DirectXTex/pull/307 and will be included in the January 2023 or later release of DirectXTex.
### Workarounds
If your code makes use of **ConvertToSinglePlane**, you can validate that the width & height alignment requirements are met for the input image before calling the function.