Document the "Show agentless resources” toggle in the Fleet UI settings

[vishaangelova]

This PR adds documentation for the "Show agentless resources” toggle in the Fleet UI settings, which was added in elastic/kibana#237528. The toggle is available in 9.1.6 and 9.2.0.

Resolves elastic/ingest-docs#1865

[vishaangelova]

This feature was added in 9.2 and it was backported to 9.1.6, so I assume having an applies_to for 9.1.6 also entails later versions as well.

[jen-huang]

I think this is correct

applying stack here does match our other documentation for agentless, but this is confusing to me because agentless is only available in ECH and serverless, it is not available for self-managed flavors (no matter if it's ECE, ECK, or regular stack)

but that's a larger cleanup effort so I'm fine with matching the rest of the documentation for now

[github-actions]

🔍 Preview links for changed docs

• reference/fleet/fleet-settings.md

[jen-huang]

Left note about self-managed environments but doesn't block this PR. Thanks!

[jen-huang]

I think this is correct

applying stack here does match our other documentation for agentless, but this is confusing to me because agentless is only available in ECH and serverless, it is not available for self-managed flavors (no matter if it's ECE, ECK, or regular stack)

but that's a larger cleanup effort so I'm fine with matching the rest of the documentation for now

[vishaangelova]

Thanks @jen-huang, I think that in the section-level and in-line applies_to syntax, we can only distinguish between the lifecycles for stateful vs stateless, I wasn’t able to limit this to ECH - this might explain why other docs also use only stack for version-specific changes in the docs regardless of the page-level deployment-specific applies_to.

@colleenmcginnis, am I right we currently cannot reference deployments in section-level and in-line applies_to? It seems to me this is one of those use cases where the use of applies_to for both version-specific changes and for deployment-specific information can confuse users (and us, as well).

[benironside]

Thank you Visha! Looks good. Left a few suggestions but nothing blocking.