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}

tools_webrtc/coverage/generate_ios_coverage_command.py

@@ -62,6 +62,7 @@ TESTS = [
   'rtc_pc_unittests',
   'rtc_stats_unittests',
   'rtc_unittests',
+  'slow_tests',
   'system_wrappers_unittests',
   'test_support_unittests',
   'tools_unittests',