Implement type key-word-argument for numba.typed.List constructor

[esc]

Since the inception of the numba.typed.List the List.empty_list factory method has been a crutch to get the code working. Originally, it was supposed to be called List.empty -- however due to "reasons" this caused a conflict with numba.typed.Dict.empty (investigation to follow) and so it now has it's current unwieldy form.

Now that numba.typed.List has a way to be initialized in a Pythonic fashion from an iterable (see: #5294), it would be nice to allow the constructor to take type (or typ or type_ to avoid naming conflicts?) as a keyword argument, so as to allow manual specification of the types. As outlined in #5716 the API would look something like:

l = List()                 # empty list with undefined type
l = List(type=int64)       # empty list with defined type
l = List(iter)             # list initialized from iter
l = List(iter, type=int64) # list initialized from iter and with items cast to given type

In addition, we may want to deprecate/rename empty_list to _empty_list since it will probably still be used under the hood. And also, some parts of the code-base may need to be updated to reflect this change. Lastly the documentation will need to be scanned and potentially updated to reflect the changes.

Note: this should also be made compatible with NUMBA_DISABLE_JIT as in this case, the keyword argument will just be ignore and a regular Python list will be returned.