Add support for appt2

[cobey]

We should migrate our build process to utilize aapt2 when available, leaving aapt as a fallback option for legacy support.

https://android.googlesource.com/platform/frameworks/base/+/android-7.0.0_r7/tools/aapt2

VS bug #593491

[pjcollins]

I'd like to remove the vs-sync tag here as we have now have an experience and user story currently tracking this task. I will remove the sync and close the corresponding bug and link to this mention on one of the parent items.