Backport of Give suggestions & remind users to use required_providers when provider not in registry into v0.15

[teamterraform]

Backport

This PR is auto-generated from #28014 to be assessed for backporting due to the inclusion of the label 0.15-backport.

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

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When a user has any module, or child module, that has a ErrRegistryProviderNotKnown error, users are often confused why they don't get inheritance from other modules.

Because Terraform explicitly loads modules as units with their own provider requirements (required_providers), and adds a suggestion of a provider "did you mean" if they have a provider of the same type (but not the default namespace) in their requirements.

This is what the new suggestion looks like in practice (with suggestion):

This is what the new suggestion looks like in practice (without suggestion/no existing provider requirements):

Open to comments on improving this suggestion to be more user-friendly (for lack of a better term)

My hope is that this can address the (very valid!) concerns and comments surrounding issues like #27920 and #27701 . In #27920, Martin suggests an improvement where we could suggest a similar-name provider we may know about, but because of how the code is currently structured, I don't have confidence in picking an accurate (successful) name, so I am suggesting a more general suggestion here.

Fixes #27920
Fixes #27701

[ghost]

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