Remove the connectivity switch from the configuration, ask preCICE

[MakisH]

preCICE v2.3.0 precice/precice#1080 introduces an API method to ask whether mesh connectivity is required. In the OpenFOAM adapter, we currently ask the user whether this is required, which the user should not need to configure, as it is system-internal information: https://precice.org/adapter-openfoam-config.html#nearest-projection-mapping

We could directly ask preCICE for this and remove the option from the configuration. As it currently defaults to false, maybe we can do it in a backwards-compatible way and deprecate the option for now.

[davidscn]

This is not trivial to implement since the location type changes when we require mesh connectivity. We could hide this complexity from the user, but a separate coupling interface is preCICE-wise a must.