`+` 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
With this commit we remove the documentation for the setting
`xpack.monitoring.collection.indices.stats.timeout` which has already
been removed in code.
Closes#32133
Relates #32229
Jake Landis
lcawl
Shaunak Kashyap
Daniel Mitterdorfer