[llvm][NFC]Refactor AutoUpgrader case 'n'.

The NVPTX intrinsics are under 'n'. Use the consume_front API, so fix
that. Refactor the helper function to group matchers on the first
component and check that first. Do similarly with the final set of
intrinsics, which have a lot of commonality in the matching.  Finally
reorder the argument/return type checking wrt name checking -- the
former is going to be cheaper, so do that first before checking the
name.#

Reviewed By: tra

Differential Revision: https://reviews.llvm.org/D158445