[bazel] Add generated test_suites
[bazel] Add generated test_suites

This allows users to build or run subsets of the tests like:

    bazel test //tests:pathops_tests

Change-Id: Ia94431879b7731257a03ae26224395e95f746680
Bug: skia:13758
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/592739
Reviewed-by: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia