Convert video quality test from a TEST_F to a TEST fixture.

The purpose is to make the fixture reusable in downstream
projects. The CL adds the following things to API:

- api/test/video_quality_test_fixture.h
- api/test/create_video_quality_test_fixture.h

The following things are moved to API:

- call/bitrate_constraints.h (api/bitrate_constraints.h)
- call/simulated_network.h (api/test/simulated_network.h)
- call/media_type.h (api/mediatypes.h)

These are required by the params struct passed to the
fixture. I didn't attempt to split the params struct into
an internal-only and public version in this CL, and as
a result we need to pull in the above things. They are
quite harmless though, so I think it's worth it in order
to avoid splitting up the test config struct.

This CL doesn't solve all the problems we need to
implement downstream tests; we probably need to upstream
tracing variants of FakeNetworkPipe for instance, but
that will come later. This puts in place the basic
structure for now.

Bug: None
Change-Id: I35e26ed126fad27bc7b2a465400291084f6ac911
Reviewed-on: https://webrtc-review.googlesource.com/69601
Commit-Queue: Patrik Höglund <phoglund@webrtc.org>
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23714}
diff --git a/video/BUILD.gn b/video/BUILD.gn
index df50d90..113caea 100644
--- a/video/BUILD.gn
+++ b/video/BUILD.gn
@@ -146,12 +146,20 @@
   }
   rtc_source_set("video_quality_test") {
     testonly = true
-    visibility = [ ":*" ]  # Only targets in this file can depend on this.
+
+    # Only targets in this file and api/ can depend on this.
+    visibility = [
+      ":*",
+      "../api:create_video_quality_test_fixture_api",
+    ]
     sources = [
       "video_quality_test.cc",
       "video_quality_test.h",
     ]
     deps = [
+      "../api:fec_controller_api",
+      "../api:video_quality_test_fixture_api",
+      "../call:fake_network",
       "../logging:rtc_event_log_api",
       "../logging:rtc_event_log_impl_output",
       "../media:rtc_audio_video",