Migrate remaining NOTREACHED()s in components/

NOTREACHED() and NOTREACHED_IN_MIGRATION() are both CHECK-fatal now.
The former is [[noreturn]] so this CL also performs dead-code removal
after the NOTREACHED().

This CL does not attempt to do additional rewrites of any surrounding
code, like:

if (!foo) {
  NOTREACHED();
}

to CHECK(foo);

Those transforms take a non-trivial amount of time (and there are
thousands of instances). Cleanup can be left as an exercise for the
reader.

Bug: 40580068
Change-Id: I72205fb77747957c6bf33dbea93656fd20085a42
Low-Coverage-Reason: OTHER Should-be-unreachable code
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6010008
Reviewed-by: Rick Byers <rbyers@chromium.org>
Owners-Override: Rick Byers <rbyers@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1382618}

components/safe_search_api/safe_search_util.cc

@@ -108,8 +108,7 @@ void ForceYouTubeRestrict(const GURL& url,
   switch (mode) {
     case YOUTUBE_RESTRICT_OFF:
     case YOUTUBE_RESTRICT_COUNT:
-      NOTREACHED_IN_MIGRATION();
-      break;
+      NOTREACHED();
 
     case YOUTUBE_RESTRICT_MODERATE:
       headers->SetHeader(kYouTubeRestrictHeaderName,