Allow formatting of .tfbackend files

[lucioreisgh]

This Pull Request enhances the terraform fmt command by enabling support for .tfbackend files. Additionally, it improves error logging by including previously unsupported file extensions.

Target Release

1.12.x

CHANGELOG entry

• This change is user-facing and I added a changelog entry.
• This change is not user-facing.

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[lucioreisgh]

@crw Im starting to contribute now to Terraform, this PR is for this issue #36564

Anything else I should do?

[crw]

Hi @lucioreisgh. The first thing you should do is read the Contributing Guide. Generally we request that the design of a change be discussed in the relevant issue before implementation if you want it to be reviewed.

In this case, given the conversation on #36570, I am going to close this PR, as it does not change or further address the problems discussed in that thread.