Partial implementation of the #430
* New endpoint structure:
* `GET /` -- a placeholder for the future home page
* `GET /catalog` -- get a list of available sources, as a list of json
blobs.
* `[{id, name, description, attribution, vector_layer}, ...]` (some
fields might be missing)
* `GET /<id>` -- get tilejson for the given source, or a combination of
sources. No `.json` extension
* `GET /<id>/<z>/<x>/<y>` -- get a tile. No format extension.
* `GET /health` -- healthcheck
* Introduce a new tile format support crate (using code from the
maplibre/mbtileserve project)
* Removed the `/rpc/...` routes - all source IDs are accessed in the
same way
* Can print auto-generated configuration or save it to a file
* Refactored to support multiple sources from multiple backends, with a
proper naming conflict resolution
TODO:
* benchmarks need to be rewritten - they were relying on some internal
structures that are no longer there. This might be done as a separate PR
due to a very different internal architecture - might need to rethink
benchmarking approaches.
