Maps: Update/fix mapTracks in NativeGeoTable and PivotedGeoTable classes

This issue is being created from this discussion: https://github.com/influxdata/giraffe/pull/578#discussion_r631937560

Basic summary is that, right now this function is only looking for `lat` and `lon` columns, which is only being used for the map type `Track Maps`. When we start implementation for `Track Maps`, we want to change the functionality to allow users to select their options for lat/lon. Based on this, we will need to fix the current implementation in `NativeGeoTable` and `PivotedGeoTable` (happens when the lat/lon can be given as fields).

Start with the discussion linked from the issue, then inspect mapTracks in the NativeGeoTable and PivotedGeoTable classes. Determine how latitude and longitude are currently selected and what behavior is required when they are provided as fields. Done means both classes support the agreed latitude/longitude selection behavior for Track Maps.

Written by the indexing model from the issue text.