[APM] POC: Add support for additional dimensions in apm rules

[sorenlouv]

This is a POC and currently only for demo purposes. Review not needed

Early POC (frontend only) for adding additional dimensions to APM rules. This aims to solve usecase 1 and three in the APM Alerting use cases.

By adding a new dimension (eg. transaction.type) the dimension will be added as a key to the multi_terms agg.
In the case of transaction.type, it will be possible to select "All", and be notified when any transaction group has a latency higher than the threshold. It will also be possible to create rules that only monitor a specific transaction group.

Note: needs design

We have three rule types in APM that will benefit from this, with the given dimensions:

• Transaction Latency
  • Dimensions: transaction.name, container.id, kubernetes.pod.name, service.version
• Failed transaction rate
  • Dimensions: transaction.name, container.id, kubernetes.pod.name, service.version
• Error count
  • Dimensions: error.grouping_key, transaction.name, container.id, kubernetes.pod.name, service.version