DEP: non-integer scalar python sequence repeat

This starts deprecation for code such as
np.float_(3.4) * [1, 2]
which should only work for integer objects. It may be possible
to just return NotImplemented since at least python sequences
implement their multiply themself through __index__.

Further action is only needed for PyArray_PyIntAsIntp, so this
is part of a larger deprecation now.

Closes gh-4036