Also adds parsing SwiftShader to the test expectations code.

Bug: angleproject:3876
Change-Id: I70e1475b62f86160d5a150218e792801fb0259bc
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1817109Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>