Add poles support in getBounds on the Globe

[stepankuzmin]

This PR adds the pole support in getBounds on the Globe. It adds a new util function polesInViewport, that detects if the poles are visible in the current viewport by intersecting the location with the viewport in screen coordinates and checking if they are behind the globe surface.

Previously the poles support was removed in #12318

Before

After

Launch Checklist

• briefly describe the changes in this PR
• include before/after visuals or gifs if this PR includes visual changes
• write tests for all new functionality
• document any changes to public APIs
• manually test the debug page
• apply changelog label ('bug', 'feature', 'docs', etc) or use the label 'skip changelog'
• add an entry inside this element for inclusion in the mapbox-gl-js changelog: <changelog>Improve poles support in getBounds when projection is set to globe</changelog>

[SnailBones]

Nice work Stepan! Just a few nits.

[karimnaaji]

@SnailBones @stepankuzmin Should we cherry-pick that fix in the beta so it's available in final?

[SnailBones]

@karimnaaji If we're doing a second beta anyway then absolutely! If we're releasing metrics in 2.12 soon, I think this could probably wait until then. I doubt it's worth the effort to go through an extra release just for this improvement

Though I'm open to different opinions if this is more critical than I think. @stepankuzmin

EDT: Misunderstood @karimnaaji`s proposal, I think this is low-risk enough that we could release it directly into the final without another beta. Though I'd be curious to your thoughts @stepankuzmin

[stepankuzmin]

This should be a low risk to push it into the final release, but this might affect the existing users with the globe enabled. So we might play safe and ship it into beta to see if there is any feedback on the new behavior. Anywise, I'm okay to push it to the final release @karimnaaji @SnailBones