Prepare to rename RTC_NOTREACHED to RTC_DCHECK_NOTREACHED

Add implementation of RTC_DCHECK_NOTREACHED equal to the RTC_NOTREACHED.
The new macros will replace the old one when old one's usage will be
removed. The idea of the renaming to provide a clear signal that this
is debug build only macros and will be stripped in the production build.

Bug: webrtc:9065
Change-Id: I4c35d8b03e74a4b3fd1ae75dba2f9c05643101db
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/237802
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Artem Titov <titovartem@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35348}
diff --git a/video/video_quality_test.cc b/video/video_quality_test.cc
index ac565cc..9fa7a98 100644
--- a/video/video_quality_test.cc
+++ b/video/video_quality_test.cc
@@ -888,9 +888,9 @@
         // aom_codec_enc_cfg_t::rc_resize_mode in Av1 encoder wrapper.
         // Until then do nothing, specially do not crash.
       } else {
-        RTC_NOTREACHED() << "Automatic scaling not supported for codec "
-                         << params_.video[video_idx].codec << ", stream "
-                         << video_idx;
+        RTC_DCHECK_NOTREACHED()
+            << "Automatic scaling not supported for codec "
+            << params_.video[video_idx].codec << ", stream " << video_idx;
       }
     } else {
       // Default mode. Single SL, no automatic_scaling,