Backport of website: Document alternatives to terraform_remote_state into v0.14

[teamterraform]

Backport

This PR is auto-generated from #26941 to be assessed for backporting due to the inclusion of the label 0.14-backport.

The below text is copied from the body of the original PR.

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For some time now we've been recommending explicitly passing data between configurations using separate resource types and data sources, rather than always using terraform_remote_state, for reasons including reducing coupling between subsystems and allowing a configuration's state snapshots to be under restrictive access controls.

However, those recommendations have so far not appeared directly in the documentation for terraform_remote_state, and have instead just been alluded to elsewhere in the documentation when discussing ways to pass data between configurations.

This change, then, is an attempt to be clear and explicit about the recommendation and to give a variety of specific examples of how to implement it. The terraform_remote_state data source page is admittedly not the most intuitive place in the information architecture (from an editor's perspective) to put a set of alternatives to it, but it does appear that this documentation page is where people most commonly end up when researching options in this area and so I've put this here in an attempt to "meet people where they are".

Possibly in a future documentation reorganization we might have an separate page specifically about sharing data between configurations, but we don't currently have time to do that bigger reorganization. If we do so later, the content on this page could potentially be replaced with a summary of the recommendation and a link to another place for the details, but the goal here is to make this information visible in the existing location people look for it, rather than blocking until there's a better place for it to live.

This also includes a small amount of editing of some existing content on the page to use terminology and style more similar to how our main configuration language documentation is written.

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This closes #18603. If we merge it, I intend to backport it immediately to the v0.14 branch in order to publish it with the forthcoming v0.14.0 release in a few weeks.

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