[X86] Cleanup some of the avx512 masked fma tests to prepare for removing and autoupgrading.

-Split cases that call 2 intrinsics in the same case.
-Remove testing mask3 and maskz intrinsics with an all ones mask. These won't be interesting after the upgrade.
-Restore test cases for some intrinsics that are marked for deletion, but haven't been deleted yet.

llvm-svn: 336408