Write tests to ensure that stack monitoring functions correctly under different kibana perms

[cachedout]

Recently an issue has surfaced wherein it is possible for a monitoring cluster and a production cluster to both have a valid license but for the stack monitoring application to be unable to determine if a license is valid.

This seems to happen in cases where there is a mismatch between the Kibana's user's role which has cluster:monitor privileges set versus a monitoring user's role which has the tighter cluster:monitor/main privilege set.

To ensure we test this appropriately, we believe that we should set the xpack.monitoring.elasticsearch.username to a user with the monitoring_user role across the board in the test runner for all functional and API tests.

[elasticmachine]

Pinging @elastic/stack-monitoring

[ycombinator]

Related: elastic/elasticsearch#38060

[chrisronline]

This is done