Adds the PowerVR VendorID into the accepted vendor list, and prevent
basic GL line emulation from being ran on PowerVR hardware as it's
not required on those platforms, yet causes CTS failures when enabled.

Fixes a variety of line failure tests across OGLES3/3.1 test suites
seen on PowerVR hardware.

Bug: angleproject:5145
Change-Id: I7383f1c09d026b8d33e6fbda66418c5f8b7f90bd
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2462094Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>