Configs to run slow_tests.

This test binary has been introduced in [1] and should be run on bots.

[1] - https://webrtc-review.googlesource.com/c/src/+/107345

Bug: webrtc:9518
Change-Id: I77e1aebd5fae73a9168f09334ac09be0e865ae90
No-Try: True
Reviewed-on: https://webrtc-review.googlesource.com/c/110701
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25614}
diff --git a/tools_webrtc/coverage/generate_coverage_command.py b/tools_webrtc/coverage/generate_coverage_command.py
index fa69117..8566668 100644
--- a/tools_webrtc/coverage/generate_coverage_command.py
+++ b/tools_webrtc/coverage/generate_coverage_command.py
@@ -22,6 +22,7 @@
   'video_engine_tests',
   'tools_unittests',
   'test_support_unittests',
+  'slow_tests',
   'system_wrappers_unittests',
   'rtc_unittests',
   'rtc_stats_unittests',