With the exception of varyings, every other qualifier can be directly
output by the translator.  This simplifies and optimizes glslang
wrapper.

Varyings' in/out qualifiers are still placed in @@ QUALIFIER macros so
glslang wrapper can remove them, if inactive, not by commenting them
out, but by turning them into global variables.

Bug: angleproject:3394
Change-Id: I9a3d18df2cfd36a38308bf8f71ac12f1e1513ece
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1998839
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>