Also:
* Replace angle-brackets around including VulkanPlatform.hpp with
double-quotes.
* Remove unused Reactor/SubmoduleCheck/gtest/gtest.h

Bug: b/144825072
Change-Id: I2b68e7861355b30f93f23983e2cb97743a1bdf25
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/44389Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>