Backport of Update workspace documentation into v1.3

[teamterraform]

Backport

This PR is auto-generated from #31849 to be assessed for backporting due to the inclusion of the label 1.3-backport.

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

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What

Update the workspaces documentation in the Language and CLI documentation sets. Specifically this PR makes the following changes:

• Pulls out the majority of the "How workspaces work" content from the language docs and puts it all together in the CLI documentation. I have added links on the language page to the CLI docs where users can find more information.
• Removes version information about very old Terraform versions from the language documentation. We have versioned docs now, so this seems unnecessary. We're also on Terraform v1.3, which is very far removed from v0.9 that the note is referring to.
• Adds headers to help break up long blocks of content and help users better find useful information.
• Clarifies when users should and should not use workspaces to manage multiple groups of infrastructure. Specifically, it appears that this is not appropriate when multiple sets of infrastructure need strong separation - access credentials, etc. Because workspaces within a working directory use the same backend, this type of separation is not possible with workspaces alone.
• Tries to make the content as short and concise as possible. Also revises it to adhere to style conventions.

Why

Users are understandably confused by the fact that we currently talk about how you can use workspaces for deployments in multiple environments but then explicitly say that this is not a recommended pattern for some deployments. It's pretty hard to understand right now what's recommended and when practitioners should be using workspaces for multiple sets of infrastructure.

Screenshots

Language Workspaces Page

CLI Workspaces Page

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[github-actions]

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