[Maps] support abortSignal for mvt requests to allowing canceling no longer needed requests

[nreese]

Elasticsearch data requested from Maps application passes abortSignal to requests so that request for no longer needed data can be canceled. MVT requests do not support abortSignal and continue to run even when the results are no longer needed because users move the the map to a new location or changed the query context.

Not canceling unneeded requests causes performance problems with elasticsearch.

[elasticmachine]

Pinging @elastic/kibana-gis (Team:Geo)

[thomasneirynck]

Aborted requests are propagating like this:

     request.events.aborted$.subscribe({
        next: () => {
          logger.warn(`request next aborted ${query.z}/${query.x}/${query.y}`);
        }
      });

verified this works, but need to put run kibana without the reverse proxy: see #37403