[Testing framework] Implement JSON view functionality for test command

[liamcervante]

This PR adds the TestJSON struct to the views package for use by the terraform test -json command.

It also adds a new function DestroySummary on the Test interface which prints out the results of the destroy operation that occurs at the end of every test file. Implementations for this are added to the already existing TestHuman struct as well as the new JSON struct.

This PR also extends the diagnostics implementation for JSONView, by allowing callers to provide additional metadata to be attached to the produced JSON entries. This is used by the test command to attach @testrun and @testfile entries to produced diagnostics to help TFC link diagnostics back to the relevant test cases.

[github-actions]

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[github-actions]

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