[Meta] Track performance metrics for cloud snapshots and master branch

As we agreed, we gonna have different load scenarios for testing snapshots and locally build Kibana: Kibana + ES hosted on worker can take higher load so it is irrelevant to compare cloud vs worker results.

We plan to proceed this way:
- monitor cloud by running daily "cloud scenario" for 8.0 (CI trigger) & 7.x (currently triggered manually)
- daily monitor master by building Kibana and using latests ES snapshot, running "local scenario" for it.
- build charts in Kibana stats to:
- track cloud snaphots performance
- track master build performance
- compare dev branch vs master

Tasks:
- define cloud scenario
- define local scenario
- set 7.x trigger on CI
- set master branch trigger on CI
- configure dashboards on build stats

Start by reviewing the planned cloud and local load scenarios and their CI triggers. Define the 8.0 and 7.x cloud runs, the master-branch snapshot run, and the build-stats dashboards; done means the triggers run as intended and the charts track cloud snapshots, master builds, and dev-versus-master performance.

Written by the indexing model from the issue text.