Add `DensifyGeodesic` trait

[grevgeny]

• [x] I agree to follow the project's code of conduct.
• [x] I added an entry to CHANGES.md if knowledge of this change could be valuable to users.

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This PR adds DensifyGeodesic trait that follows logic similar to DensifyHaversine. However, the trait is only implemented for T = f64 as underlying Geodesic traits are implemented only for this type.

[grevgeny]

@michaelkirk thanks for your review! I have added proposed changes

[michaelkirk]

I think you'll need to run cargo fmt, otherwise LGTM

I'll leave it open for a couple days before merging in case anyone else wants to weigh in.

[grevgeny]

@michaelkirk

I've just realised that there is already the following method: geodesic_intermediate_fill. It expresses pretty much the same logic.

Do we still need this another implementation?

[michaelkirk]

Darn it. I'm sorry for not realizing this earlier. This seems related to https://github.com/georust/geo/issues/1181

[michaelkirk]

Assuming #1216 gets merged, I've got a different approach that should supersede this, generically implementing Densify for all line measures (Haversine, Geodesic, Euclidean, etc.)

You can see a WIP here: https://github.com/georust/geo/compare/mkirk/unify-densify?expand=1

[michaelkirk]

My alternative to this was merged in #1231.

With that you can call:

use geo::{Geodesic, Densify, Euclidean};
line_string.densify::<Geodesic>();
line_string.densify::<Euclidean>();

Let me know if that works for your purposes @grevgeny.

[michaelkirk]

With #1298 (not yet released) this changed to:

use geo::{Geodesic, Densify, Euclidean};
Geodesic.densify(&line_string);
Euclidean.densify(&line_string);