Refactor the dEQP runner functions into a package so that others can
re-use them.

Change-Id: Ia9c92ca708c3f17a87687c2627843922a8c27514
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/38812
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Tested-by: Paul Thomson <paulthomson@google.com>