[codegen] Don't return after CSA_CHECK failures

Changes FastCheck failures to just call Unreachable (which in turn
calls DebugBreak) instead of DebugBreak and then returning to just
after the check. FastCheck is only called in release builds so this
does not affect debug builds.

This reduces the embedded instruction size from 1249720 to 1246812
(2908 bytes) for ARM.

Change-Id: If4b9b6810a53d64262a0fa9c2a1903e022748a22
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2002538Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Dan Elphick <delphick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65803}

src/codegen/code-stub-assembler.cc

@@ -280,10 +280,7 @@ void CodeStubAssembler::FastCheck(TNode<BoolT> condition) {
   Label ok(this), not_ok(this, Label::kDeferred);
   Branch(condition, &ok, &not_ok);
   BIND(&not_ok);
-  {
-    DebugBreak();
-    Goto(&ok);
-  }
+  Unreachable();
   BIND(&ok);
 }