Consider scalability / load test for MP specs

[rsvoboda]

Consider scalability / load test for MP specs.

There are several aspects to this topic:

• load simulating production use - stable load aka flat mode
• load simulating production use - variable load aka peaks during the day
• load simulating dev use - reloads, apps deploy / undeploy, invalid applications
• for scalability certain specs can be more sensitive - e.g. metrics, health, ft

Implementation is to be decided, definitely new TS or at least new module.
Even more TS can be considered for different use-cases / aspects.

[mnovak]

This is testing gap we have and can be processed by MP specs updates and incorporated into new test development for those specs. For now setting minor priority but it can be changed in the future.