[fir] Add fir.select and fir.select_rank FIR to LLVM IR conversion patterns

The `fir.select` and `fir.select_rank` are lowered to llvm.switch.

This patch is part of the upstreaming effort from fir-dev branch.

Reviewed By: mehdi_amini

Differential Revision: https://reviews.llvm.org/D113089



Co-authored-by: Jean Perier <jperier@nvidia.com>
Co-authored-by: Eric Schweitz <eschweitz@nvidia.com>