metric dimensions are increasingly important as we migrate metrics integrations to TSDS (time series data streams).

We must not only mark specific fields as metric dimensions, but we must also be mindful of the number of individual dimension fields in the metric document (ES has a hard limit on the number of allowed dimensions).

many (all?) AWS datastreams include a aws.dimensions.* mapping e.g. https://github.com/elastic/integrations/blob/main/packages/aws/data_stream/ebs/fields/package-fields.yml#L12. in addition to these wildcard mappings, we should explicitly name each dimension field we are using to group by e.g. . https://github.com/elastic/integrations/blob/main/packages/aws/data_stream/ebs/fields/fields.yml#L4-L10. this also allows us to specify the individual dimensions for TSDS.