Support geospatial queries

[avelino]

https://docs.mongodb.com/manual/geospatial-queries/

We don't know how many MongoDB users use geospatial queries. Please vote for that issue if you need them.

### Tasks
- [ ] #3193
- [ ] https://github.com/FerretDB/FerretDB/issues/4206

[AlekSi]

We probably could use PostGIS. But that's a big task anyway.

[DblK]

And also SpatiaLite for SQLite since you add this new backend.