[DOCS] Added monitoring PRs to 6.1 release notes (elastic/x-pack-elasticsearch#3297)
[DOCS] Added monitoring PRs to 6.1 release notes (elastic/x-pack-elasticsearch#3297)

* [DOCS] Added monitoring PRs to 6.1 release notes

* [DOCS] Merged release note content

Original commit: elastic/x-pack-elasticsearch@bc7f95959002d089f3790d1871c37f8fce731e80

strapdata/elassandra,strapdata/elassandra,vroyer/elassandra,vroyer/elassandra,strapdata/elassandra,vroyer/elassandra,strapdata/elassandra,strapdata/elassandra