Vulkan: Refactor ID-discovery out of SPIR-V transformer
Vulkan: Refactor ID-discovery out of SPIR-V transformer

The SPIR-V transformer performs multiple transformations in one pass.
This is the first of a series of refactoring changes that detangle these
transformations and encapsulate them, while allowing the transformation
to remain single-pass.

Bug: angleproject:4888
Change-Id: I327f693d99496a0b89028abe627119e4a2b07c42
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2702651
Reviewed-by: Charlie Lao <2661ca4ca24c371418789adbc76dfb4875087223@google.com>
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Commit-Queue: Shahbaz Youssefi <582eeec4f08a2ccd61e3ef52115e6e7c571582de@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle