Data provider: add option to tell a data server has no mirror data

SPARQL queries can be quite long because we are also looking for data in the `http://semapps.org/mirror` graph.

But in some cases, for example with ActivityPods, we don't use this graph at all, so queries could be simplified.

We could add a `noMirrorData` option to the data servers to tell the data provider not to bother looking at this graph.

(Note: This would be a temporary fix, because when all resources will have their own named graph, we will remove this mirror graph)

Locate the data provider and data server configuration, then inspect where SPARQL queries include the http://semapps.org/mirror graph. The work is done when a noMirrorData option prevents that graph from being queried for configured servers while the existing behavior remains unchanged by default.

Written by the indexing model from the issue text.