Change instance specific dimensions in aggregated metrics

Currently, instance specific metrics are part of the transaction metrics dimensions, and can lead to time series explosion.

To reduce the number of transaction metric timeseries, we remove the instance-specific dimensions and introduce a new metric set that has instance specific dimensions but not `transaction.name`.

Required changes:
- review dimensions and propose which ones classify as instance-specific
- remove the instance dimensions from transaction metrics
- create a new metric set with instance dimensions
- update documentation
- update apmpackage