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>