Add maputils function to fully pixelate a coordinate path

[ayshih]

This PR adds a new maputils function – pixelate_coord_path() – that fully pixelates a coordinate path. extract_along_coord() tries to do that, but has issues (see #6826 and #6802). Here's a comparison of the pixel paths:

TODO:

• Add a unit test
• Deprecate extract_along_coord()
• Update examples
• Add a changelog entry
• Add a note that a path passing through a four-corners point may not pick up all four pixels due to floating-point comparisons

[wtbarnes]

The plot showing the comparison of the two approaches in the first comment could make a good "How-to-Guide" entry.

[ayshih]

The plot showing the comparison of the two approaches in the first comment could make a good "How-to-Guide" entry.

Er, I'd say an "explanation" page. The how-to guide would just say how to pick different line algorithms.

[nabobalis]

Failure looks like a example broken for pandas 2.0.