Add deployment considerations to the Heartbeat docs

[dedemorton]

Describe the enhancement:

We are currently streamlining the content in the Observability Guide to remove duplicated content about Beats (specifically the getting started content about ingesting data). The content that we are removing contains deployment considerations for Heartbeat that AFAIK are not covered in the Heartbeat docs.

I'm opening this issue to raise awareness. I can help you get this content into the Heartbeat docs, but would like confirmation that this documentation should be included.

Someone needs to review the content (intro and deployment considerations) in the existing (old) topic and determine if it should be copied over to the Heartbeat docs.

The PR that removes the content is here. The current plan is to backport this PR to 8.7 and later, so you might need to look at 8.6 to see the original file.

[elasticmachine]

Pinging @elastic/obs-docs (Team:Docs)

[nimarezainia]

@drewpost Someone from your team probably would need to review these before changes are made.

[botelastic[bot]]

Hi! We just realized that we haven't looked into this issue in a while. We're sorry!

We're labeling this issue as Stale to make it hit our filters and make sure we get back to it as soon as possible. In the meantime, it'd be extremely helpful if you could take a look at it as well and confirm its relevance. A simple comment with a nice emoji will be enough :+1. Thank you for your contribution!