Chunking apply_fun for MCState.to_array (#1470)

`MCState.to_array()` cannot be used to instantiate the wave function
over the full Hilbert space for systems with fairly large size (but that
should be still accessible) due to a large memory usage. The
modification in `MCState.to_array()` consists in the possibility of
computing the wave function over chunks of the Hilbert space of size
`MCState.chunk_size` that are then combined to get the complete state
vector.

---------

Co-authored-by: Clemens Giuliani <clemens@inailuig.it>