Revert "[VectorUtils] Introduce the Vector Function Database (VFDatabase)."

Revert "[VectorUtils] Introduce the Vector Function Database (VFDatabase)."

This reverts commit 0be81968a283fd4161cb9ac9748d5ed200926292.

The VFDatabase needs some rework to be able to handle vectorization
and subsequent scalarization of intrinsics in out-of-tree versions of
the compiler. For more details, see the discussion in
https://reviews.llvm.org/D67572.