schema: Fix schema merging for terraform_remote_state data source

[radeksimko]

Originally reported in hashicorp/vscode-terraform#1575

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When implementing the fix in #251 we forgot to account for other parts of the terraform_remote_state schema which come in the form of provider schema, namely workspace, defaults and outputs.

[jpogran]

🚢

[jsinme]

I'm having an issue where the syntax highlighter is complaining about the config block in the terraform_remote_state data source: Unexpected attribute: An attribute named "config" is not expected here
I reverted to v2.27.2 and the error went away so I believe there is still an issue with the schema here
I will attempt to take a look and contribute a fix, but this is my first interaction with this code base so someone else may be able to find and resolve this quicker

[radeksimko]

@jsinme We are aware of this, it's a different bug which we're tracking in hashicorp/vscode-terraform#1580