Account for finite pixel size in PointPixelRegion.contains

Currently the `PointPixelRegion.contains` method [always returns `False`](https://github.com/astropy/regions/blob/main/regions/shapes/point.py#L81). However this is not correct for the cases of sampled image data, because the size of the pixel is finite, namely `1 x 1 pix`. This mean the `.contains()` method should return true if a position is contained in the finite support of the pixel.

Start by reading regions/shapes/point.py at PointPixelRegion.contains, currently identified at line 81, and inspect the surrounding point-region behavior. The work is done when contains accounts for the finite 1 x 1 pixel support in sampled image data rather than always returning False.

Written by the indexing model from the issue text.