Request GeoJSON by deault for feature services

[patrickarlt]

Describe the problem

As discussed in https://github.com/Esri/esri-leaflet/pull/1372#pullrequestreview-1662593212 and https://github.com/Esri/esri-leaflet/issues/1373 there are lots of cases where features are requested before we know if the service supports GeoJSON or not. This introduces to performance issues because browsers have to convert to GeoJSON when we could probably have the service do it.

Describe the proposed solution

Since GeoJSON output is available since server 10.4 (which is deprecated in Feb 2022) we can probably make isModern the default for feature services.

Alternatives considered

This was discussed in https://github.com/Esri/esri-leaflet/pull/1372 but was deemed to complex to implement.

Additional Information

No response