This reverts commit 3d39b7c5.

Reason for revert: Fixed interaction with the
`forceDriverUniformOverSpecConst` workaround.

Original change's description:
> Revert "Vulkan: Generate gl_Position pre-rotation in SPIR-V"
>
> This reverts commit 0f86b196.
>
> Reason for revert:
> Breaks pre-rotation for all apps, so they are displayed in portrait instead of landscape.
>
> Original change's description:
> > Vulkan: Generate gl_Position pre-rotation in SPIR-V
> >
> > Instead of having the translator output pre-rotation code in the vertex
> > stage based on a specialization constant, this change makes the SPIR-V
> > transformer perform pre-rotation of gl_Position on the last geometry
> > stage.
> >
> > An alternative solution would be to generate pre-rotation code in the
> > translator in every geometry stage, each controlled by a separate
> > specialization constant.  This change avoids unnecessary modifications
> > to earlier stages.  The generated shaders are also smaller, as they
> > don't contain a mat2[8] pre-rotation constant matrix.  The SPIR-V
> > transformer knows the pre-rotation at transformation time, so it can
> > simply use swizzles to achieve the same results.
> >
> > This also ties in with upcoming changes which move gl_Position.z
> > correction to the last geometry shader stage, which is trivially done
> > piggy-backing on the infrastructure in this change.
> >
> > Bug: angleproject:5478
> > Change-Id: I9d5d9d19f3ccda665f5504368ce5ddfa5f383faf
> > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2598584
> > Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
> > Reviewed-by: Charlie Lao <cclao@google.com>
> > Reviewed-by: Jamie Madill <jmadill@chromium.org>
>
> TBR=syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com
>
> Change-Id: I81f237fa6b10c7d59831363bee8999e7ad2f09be
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: angleproject:5478
> Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2633694
> Reviewed-by: Tim Van Patten <timvp@google.com>
> Commit-Queue: Tim Van Patten <timvp@google.com>

TBR=timvp@google.com,syoussefi@chromium.org,jmadill@chromium.org,cclao@google.com

Bug: angleproject:5478
Change-Id: I7c5eaeef03d9520abd36a1c4a766b6abbf4fdb45
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2633709Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>