WebGPU: Run dEQP GLES2 tests. Add the flags and platform support needed to initialze the WebGPU backend. Set up initial test expectations with broad suppressions. Current pass rate: 14.27% Bug: angleproject:356399840 Change-Id: I1339cd978ca75b59a2e99ee81d93981dc6066f36 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5751601 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>