RoI should be able to determine if points lie within them

[willGraham01]

Subtask of #377.

A region of interest should be able to determine whether a point (x, y) lies within the region. I had a go with this in #390 before the scope drift, so there's some relevant code here to start from.

Key things to bear in mind are how the underlying shapely objects treat the terms "inside", "on", and "contains". In particular, the shapely is_inside method does not include the boundary, but I imagine most of our users will want the boundary included by default, or at least the option to toggle it off.

As such, I envision a method being added to the BaseRegionOfInterest class that has the following signature:

class BaseRegionOfInterest:

    def point_is_inside(self, xy_position, include_boundary=True) -> bool:
        # Likely some calls to shapely commands

Once the broadcasting decorator #397 is added, this method can be decorated with the broadcastable_classmethod decorator too. (Whether we do this in the same PR that introduces the point_is_inside method will depend on if #397 is merged beforehand).