Alter internal structure of `geom.Geometry` type to allow deep equals comparisons

[peterstace]

Idea:

• Right now, we can't used deep equals style comparisons (e.g. like those from stretchr/testify) to check if two geom.Geometry values are equal. This is because there's an unsafe pointer inside the geometry.
• Consider altering the internal structure of geom.Geometry such that deep equals will "just work".