[Fleet] Link to documentation on how to set data retention/ILM policies

[jen-huang]

We are still exploring the best path forward for full support of ILM configuration within Fleet/Integrations. In the meantime, we can link users to documentation (elastic/observability-docs#986) from within the policy editor so that they can do it manually.

The current proposed UI is having it under Integration Settings > Advanced, under Namespace, some text that says:

Data retention settings
By default all logs and metrics data are stored within the hot phase. [Learn more] about changing the data retention policy for this integration.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[jen-huang]

@jethr0null @mostlyjason Please help with editing the copy :)

[mostlyjason]

@jethr0null @gjones did we ever decide on whether to call it data retention or ILM policy?

[jethr0null]

I might say something like "stored on the hot tier" (vs. phase).

I'm actually not sure what the latest is on the data retention vs ILM naming front and will defer to @gjones for an update there.

[hop-dev]

@mostlyjason here is my first go, any feedback welcome: