Added Alertmanager and 8.0 alerts content to What's New (#34925)
Added Alertmanager and 8.0 alerts content to What's New (#34925)

* Added Alertmanager and alerts docmentation

* Update docs/sources/whatsnew/whats-new-in-v8-0.md

Co-authored-by: Diana Payton <ee24b2c2426ceb8f7f9d3f1e01be1306fa31b8a1@users.noreply.github.com>

* Update docs/sources/whatsnew/whats-new-in-v8-0.md

Co-authored-by: David Parrott <e5e041851e2a25d8e9ce8fcaf277cbc0b3182a6d@gmail.com>

Co-authored-by: Diana Payton <ee24b2c2426ceb8f7f9d3f1e01be1306fa31b8a1@users.noreply.github.com>
Co-authored-by: David Parrott <e5e041851e2a25d8e9ce8fcaf277cbc0b3182a6d@gmail.com>
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