Change how start and end addresses of young strings are retrieved

This CL changes how the start and end address for the iteration are
retrieved from an std::vector that won't cause a failed assertion.

There are some std::vector implementations that contain bounds checks.
The string table iteration code uses an access like
{&young_strings_[young_strings_.size()]} to retrieve the end address
for an iteration. This results in a out of bounds exception on such a
std::vector implementation even though the "element" itself is not actually
accessed.

Change-Id: I31db8994a7ff613897ad9deac953a1ee91f322b3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1704097Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62742}

src/heap/heap.cc

@@ -2576,8 +2576,8 @@ void Heap::ExternalStringTable::IterateYoung(RootVisitor* v) {
   if (!young_strings_.empty()) {
     v->VisitRootPointers(
         Root::kExternalStringsTable, nullptr,
-        FullObjectSlot(&young_strings_[0]),
-        FullObjectSlot(&young_strings_[young_strings_.size()]));
+        FullObjectSlot(young_strings_.data()),
+        FullObjectSlot(young_strings_.data() + young_strings_.size()));
   }
 }