WGSL: implement inc/dec with generated functions Implements inc/dec with generated WGSL functions that take pointers and perform a post/pre inc/decrement. This works with scalars, vectors, and matrices, both float and int. WGSL supports inc/dec only on integer types, and only as statements (not as expressions). https://www.w3.org/TR/WGSL/#increment-decrement. The regular ++ and -- are used in this specific case. The WGSL outputter records usage of increment/decrement and produces a call to the correct function. A new class is introduced to keep the record of which types need generated inc/dec WGSL functions. Bug: angleproject:42267100 Change-Id: I0e70760ba5bd00f978e216f958216ae3137a146e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6935269 Commit-Queue: Matthew Denton <mpdenton@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>