Revert "Always include public/include headers for vulkan and just guard src files with SK_VULKAN."

This reverts commit 6e2d607334cc57c22e3a52179743763828ea84b2.

Reason for revert: chrome roll

Original change's description:
> Always include public/include headers for vulkan and just guard src files with SK_VULKAN.
> 
> This should allow a client to build a skia library that doesn't use vulkan but still
> has all the public headers defined so that they don't have to build two versions of
> their code.
> 
> Bug: chromium:862144
> Change-Id: I0eecbe0bc48123619f217e2cf318eb9a8c77ccb2
> Reviewed-on: https://skia-review.googlesource.com/158661
> Reviewed-by: Brian Salomon <bsalomon@google.com>
> Commit-Queue: Greg Daniel <egdaniel@google.com>

TBR=egdaniel@google.com,bsalomon@google.com,cblume@chromium.org

Change-Id: I76ae6f435333755fa5d546fc1e5999a324b4fd05
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:862144
Reviewed-on: https://skia-review.googlesource.com/c/159000
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
7 files changed