resourceloader: Enforce strict string keys in mw.Map
* No longer perform any key-to-string casting in get(), set(),
or exists().
- Setting a non-string key is ignored.
- Looking for a non-string key that looks like a string key
that exists will not find it.
Clean up:
* Remove needless `selection=slice.call(selection)` in mw.Map#get
Follows-up
77d71f743 (r75486). Not sure why this was here.
* Inline logic for the multi-key retrieval instead of recursing.
This also removes undocumented behaviour where a nested array
could be passed to mw.config.get(), e.g. mw.config.get([['debug']]),
which would produces a nested object.
Change-Id: I84506930919e59ce16d96d6d623db5aae5f273e1