It's a PITA to create a new local `Distribution`

We should make it easier to make a new local `Distribution` -- perhaps allow creating a new distribution from an existing distribution.

This comes up when a new local arrays are created that don't match the distribution of the originating array -- perhaps the local shape changes, or the local ndims. `local.maps.Distribution` could have a classmethod like `from_distribution` that would take an existing distribution for the defaults and allow passing in `new_shape`, `new_dist` and `new_grid_shape` args that would set the appropriate values. There may need to be global communication to support this.