Test Runner: Add a slow tests list. Each slow test in the list will use a 3x longer timeout. The list is implemented using the same filter wildcard we use in the test expectations logic. We can test this out using a slow D3D11 varying test. Bug: angleproject:5076 Bug: angleproject:5496 Change-Id: I31cf45e6ee8a8bbd6e460d675ff8a0cf5f19a504 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2625172 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>