Implement State, State.Get, State.GetAttribute, Config, Plan

[kmoe]

The changes to internal/reflect on main made rather a mess of katystate3. We're up to katystate5 now.

The main work here is the addition of ApplyTerraform5AttributePathStep to all schema types, implementing the tftypes.AttributePathStepper interface so that we can traverse the schema with tftypes.WalkAttributePath.

[kmoe]

It turns out that nested attributes did not need the AttributePathStepper implementation, at least if we want to represent (for example) ListNestedAttributes as a types.ListType. Instead, the schema and its nested attribute types get a recursive AttributeType() method, which returns a reasonable attr.Type representation. This is needed in any case for State.Get.

Please take a look at the tests to see if this provides the appropriate UX.

[paddycarver]

Some minor feedback on this one. I think the only part that's super important is the object using the wrong attribute path step type.

[paddycarver]

Let's do it. 🚀

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.