Use JIT compiler to back `cupy.fromfunction()`

### Description

#5925 added a bunch of NumPy-compliant functions, including `cupy.fromfunction()`. However, it is suboptimal as `numpy.fromfunction` is called internally.

It'd be nice to take the same JIT capability behind `cupy.vectorize()` and make it work with `fromfunction`. However, a common usage of `fromfunction` [seems to involve lambda functions](https://numpy.org/doc/stable/reference/generated/numpy.fromfunction.html), which CuPy does not support yet (#4290). Not sure if this is a blocker, though.

### Additional Information

_No response_

Start by reading the cupy.fromfunction implementation added in #5925 and the JIT path behind cupy.vectorize(); compare their behavior with numpy.fromfunction, including the lambda limitation tracked in #4290. Done means fromfunction no longer relies on numpy.fromfunction internally and its supported behavior is covered by appropriate tests.

Written by the indexing model from the issue text.