Vulkan: Factor out DriverUniform code to tree_utils/DriverUniform.cpp The driver uniform code is used by various tree_ops functions. But all driver uniform code are defined and implemented in the TranslatorVulkan.cpp file. There is dependency rule that tree_ops code can not call into vulkan specific function. Right now we are working around this problem by always having TranslatorVulkan creates uniform and pass it down to tree_ops. This creates inefficiency for cases that dFdy/dFdx where we don't know if we will need the driver uniform or not, until we walk the tree and see the dFdx node. This CL refactors driver uniform code into its own file and class under tree_utils so that everybody can use. Mean time we can also make it much easier for metal to expand it to have its own uniform structure. Bug: b/173047182 Change-Id: I06bd9a005ccd6dc0a21321a3010dda1eab9d6fdb Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2533443 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com>