[Inventory] Update EEM docs to reflect new inventory

[alaudazzi]

Description

This PR updates the EEM docs to:

a) include more entities: services, hosts and containers
b) remove references to the 'new service inventory' and instead mention the 'new inventory'

References to Inventory will work as soon as the new Inventory doc page is live with #4341.

Documentation sets edited in this PR

Check all that apply.

• Stateful (docs/en/observability/*)
• Serverless (docs/en/serverless/*)
• Integrations Developer Guide (docs/en/integrations/*)
• None of the above

Related issue

Closes #4253

Checklist

• Product/Engineering Review
• Writer Review

Follow-up tasks

Select one.

• This PR does not need to be ported to another doc set because:
  • The concepts in this PR only apply to one doc set (serverless or stateful)
  • The PR contains edits to both doc sets (serverless and stateful)
• This PR needs to be ported to another doc set:
  • Port to stateful docs: <link to PR or tracking issue>
  • Port to serverless docs: <link to PR or tracking issue>

[mergify]

This pull request does not have a backport label. Could you fix it @alaudazzi? 🙏
To fixup this pull request, you need to add the backport labels for the needed
branches, such as:

• backport-/d./d is the label to automatically backport to the /d./d branch. /d is the digit
  NOTE: backport-skip has been added to this pull request.

[roshan-elastic]

Hey @alaudazzi,

Looks good - just one change:

During Technical Preview, the Elastic Entity Model is enabled when you turn on the entity-centric service inventory described in .

You can enable the Elastic Entity Model from the [New Inventory](INSERT LINK).

Note: If already enabled, you will not be prompted to enable the Elastic Entity Model

[elasticdocs]

🚀 Built elastic-dot-co-docs-preview-docs successfully!

• https://elastic-dot-co-docs-production-ajdm6tpvn-elastic-dev.vercel.app

• Built with commit 3fe8a98

Issues? Visit #next-docs in Slack

[alaudazzi]

@roshan-elastic I integrated your last feedback (doc preview). Waiting for your ✅ to merge.

[roshan-elastic]

approved!