tests: Remove problematical KHR_mnt1 check
tests: Remove problematical KHR_mnt1 check

Remove KHR_Maintenance1 check and conditional code from test
CopyImageTypeExtentMismatch(). Disable two clauses that are
specific to the extension, for the time being. Update the VU
database to replace missing test names.

Change-Id: I0c1442b943c3ed8a105b771868946ae68e543b50

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools