[Meta][Fleet] Add support for progressive or canary deployments

[mostlyjason]

With standalone Elastic Agent and Beats you can deploy configuration files progressively using third party solutions. Fleet does not have a feature to deploy a policy update progressively. Users could manually do it by updating agent policies but its not very convenient. We should provide a capability to test an agent policy update on a subset of agents, and then promote it to a larger group once we are confident it works well.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[rdrgporto]

Hi,

Any updates on this?

Thanks in advance ☺️,

Regards