Do not crash if codec is not available

Check if codec was successfully created and exit from RunTest if not
before creating VideoProcessor.

Bug: none
Change-Id: Ia6d7171650dbc9824fb78f4a8e2851f755cfd63b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/209362
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33372}

modules/video_coding/BUILD.gn

@@ -816,7 +816,10 @@ if (rtc_include_tests) {
       "../../test:video_test_common",
       "../../test:video_test_support",
     ]
-    absl_deps = [ "//third_party/abseil-cpp/absl/types:optional" ]
+    absl_deps = [
+      "//third_party/abseil-cpp/absl/strings:strings",
+      "//third_party/abseil-cpp/absl/types:optional",
+    ]
   }
 
   rtc_library("videocodec_test_stats_impl") {