`+` for index name inclusions is no longer supported for 6.x+. This
commit removes references of the `+` from the documenation. System
indices additional example is also included.
fixes#37237
* Implement xpack.monitoring.elasticsearch.collection.enabled setting
* Fixing line lengths
* Updating constructor calls in test
* Removing unused import
* Fixing line lengths in test classes
* Make monitoringService.isElasticsearchCollectionEnabled() return true for tests
* Remove wrong expectation
* Adding unit tests for new flag to be false
* Fixing line wrapping/indentation for better readability
* Adding docs
* Fixing logic in ClusterStatsCollector::shouldCollect
* Rebasing with master and resolving conflicts
* Simplifying implementation by gating scheduling
* Doc fixes / improvements
* Making methods package private
* Fixing wording
* Fixing method access
* Adding new MonitoredSystem for APM server
* Teaching Monitoring template utils about APM server monitoring indices
* Documenting new monitoring index for APM server
* Adding monitoring index template for APM server
* Copy pasta typo
* Removing metrics.libbeat.config section from mapping
* Adding built-in user and role for APM server user
* Actually define the role :)
* Adding missing import
* Removing index template and system ID for apm server
* Shortening line lengths
* Updating expected number of built-in users in integration test
* Removing "system" from role and user names
* Rearranging users to make tests pass
Jake Landis
Lisa Cawley
David Roberts
Shaunak Kashyap
lipsill