Add terraform query subcommand (TF-25494)

[dbanck]

WIP

Target Release

1.13.x

Rollback Plan

• If a change needs to be reverted, we will roll out an update to the code within 7 days.

Changes to Security Controls

Are there any changes to security controls (access controls, encryption, logging) in this pull request? If so, explain.

CHANGELOG entry

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

[liamcervante]

just some very early thoughts that jumped out to me - don't need to be addressed properly yet or anything.

[liamcervante]

Suggested change

	Results cty.Value
	Results []cty.Value

Since this must be a slice / tuple - is it perhaps more clear to just not include that part in the cty encoding? This makes it totally unambiguous that this is a list of things.

[dbanck]

Currently we're storing the result in the following form:

cty.ObjectVal(map[string]cty.Value{"data": cty.TupleVal(results), "config": config})

This matches the schema and makes encoding/decoding easy, but I guess we really only need the tuple val in the plan 🤔

[liamcervante]

metanote: because of the way things might change over time this may eventually become a list of structs in which one of the things that it might contain is the value. We might add some metadata about the query results (like you see in the ResourceInstanceChange for example.

This representation can change as it likes (as it is internal only) but eventually this will go into the jsonplan package which has to be more backwards compatible. At that point - I'd pre-emptively add this into a json object instead of just adding the value directly. This makes it easier to add metadata in the future, as it wouldn't be a breaking change.

You could also do that here as well, to keep the internal and external representations closer together. But, that is totally optional for here, but definitely something you should consider for the external representation.