There's a `Map::IsDictionaryMap()` method in addition to the
`Map::is_dictionary_map()`, which apparently do very different things:
The former checks whether the instance type of the Map is in a certain
range (FIRST_DICTIONARY_TYPE to LAST_DICTIONARY_TYPE), while the latter
checks the `is_dictionary_map` bit (which means that the backing store
for the properties of a JSObject is in slow mode). To make matters worse
there's also `CodeStubAssembler::IsDictionaryMap()`, which does the bit
check similar to `Map::is_dictionary_map()`. And to make matters even
worse the FIRST_DICTIONARY_TYPE to LAST_DICTIONARY_TYPE range also
contains instance types for classes that aren't subclass of `Dictionary`
(despite a comment stating the opposite).

So in conclusion it's best to remove the confusing
`Map::IsDictionaryMap()` method, which is anyways wrong, and just test
explicitly for `NameDictionary`, `NumberDictionary` or
`GlobalDictionary` in the appropriate places.

Bug: v8:9183
Change-Id: If35f73261e3cc96938ebf499bf32be3ec725288b
Cq-Include-Trybots: luci.chromium.try:linux-rel,win7-rel
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1627330
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61770}