builtins: implement ST_Angle

[erikgrinaker]

Release note (sql change): Implement the geometry builtin ST_Angle

Closes #48866.
Closes #48867.

[blathers-crl]

Thank you for contributing to CockroachDB. Please ensure you have followed the guidelines for creating a PR.

My owl senses detect your PR is good for review. Please keep an eye out for any test failures in CI.

I have added a few people who may be able to assist in reviewing:

• @otan (author of geo/geomfn: implement ST_Angle({geometry,geometry}) #48866, author of geo/geomfn: implement ST_Angle({geometry,geometry,geometry,geometry}) #48867)

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is otan.}

[cockroach-teamcity]

This change is 

[blathers-crl]

Thank you for updating your pull request.

My owl senses detect your PR is good for review. Please keep an eye out for any test failures in CI.

_{🦉 Hoot! I am a Blathers, a bot for CockroachDB. My owner is otan.}

[otan]

thanks!

bors r+

[craig]

Build failed (retrying...):

• GitHub CI (Cockroach)

[craig]

This PR was included in a batch that was canceled, it will be automatically retried

[craig]

Build succeeded:

• GitHub CI (Cockroach)