feat(bq|transformations): Point on surface functionality for BQ

[vehrka]

Description

This is a PR for the Point on Surface tool for the Analytic Toolbox for BQ.

This tool gives a point close to the centroid but makes sure it's always inside the polygon. With the centroid, sometimes it's outside the polygon, like with semicircular or circular shapes, rings, or holes within.

The Point on Surface always gives a point inside the polygon. This is Postgres' implementation and explanation https://postgis.net/docs/ST_PointOnSurface.html .

Type of change

• Feature

Acceptance

Please describe how to validate the feature or fix

1. with a polygon that has the centroid laying outside of the interior of the polygon
2. run the function to get a point that is inside of the polygon
3. the point should be inside the polygon

Basic checklist

• Good PR name
• Shortcut link (not necessary)
• Just one issue per PR
• GitHub labels
• Proper status & reviewers
• Tests
• Documentation

[Jesus89]

Nice contribution!

LGTM