Revert "Vulkan: Switch loader to new driver files env var." This reverts commit 1f6123d55467c2af7c67405c0101a6f327b76225. Reason for revert: Seems to break ANGLE on fuchsia loader: https://ci.chromium.org/ui/p/chromium/builders/try/fuchsia_arm64/1123629/overview Original change's description: > Vulkan: Switch loader to new driver files env var. > > VK_DRIVER_FILES replaces VK_ICD_FILENAMES. > > Bug: angleproject:7095 > Change-Id: I949ac9a8f375240b6c6068825eccc645f81b0185 > Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3522821 > Reviewed-by: Ian Elliott <ianelliott@google.com> > Reviewed-by: Yuxin Hu <yuxinhu@google.com> > Commit-Queue: Jamie Madill <jmadill@chromium.org> Bug: angleproject:7095 Change-Id: I5b7e094b08d76b9c14adb4acb3b59e4cfb7a28fa Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3580980 Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>