[Fleet] Filter agents per namespace.

[s-karberg]

Describe the feature:
In the UI for Fleet, you have following drop downs/buttons:

• Status
• Tags
• Agent Policy
• Upgrade available

It could be really nice to have another drop down that is e.g. named Namespaces that shows all namespaces you have added.

Describe a specific use case for the feature:

Let's say you have XX namespaces and each namespace has Y++ amount of agents in.
If you would need to do work on those agents you would need to leverage tag system or even policy, but policies ha N+1 so could be relatively many where each agent is under namespaces.

So it could be really cool to sort and view agents only based on namespace.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)