Create dashboards to monitor APM-Server SLOs over a weekly compliance period

### Motivation
SLOs provide tools that could be utilised to balance reliability and development velocities. SLOs coupled with error budget help maintain a healthy service and provide transparent performance goals for a service.

The final goal is to establish an error budget framework to objectively reason about the performance of APM-Server for the soak testing setup.

### Goals
As a first step towards this goal, create a dashboard to monitor the following SLOs for APM Server over a sliding window of weekly (7 days) compliance period:

1. Availability SLO: 99.9% good requests
2. Latency SLO: 99.9% successful requests with threshold < 1 second
3. Coverage SLO: 99.999% events successfully sent to ES
4. Throughput SLO: TBD (will depend on the generated workload)