infra: Add trace tests to CQ conditionally. This will add the trace tests with the "libANGLE/capture/" folder changes. This will prevent slow trace tests from clogging the CQ on unrelated changes, while still providing some regression testing. Bug: angleproject:5530 Change-Id: I76361aaa51c49c84dab8be7d74f4bad0db7d2419 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2686438 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Yuly Novikov <ynovikov@chromium.org>