Fix crash when nested data blocks are mixed with the import command

[liamcervante]

This PR fixes a crash that occurs when the terraform import command is used against configuration that has a nested data block defined within a check block.

Essentially, the nested data block still tries to report its checkable status during an import operation. This results in the checks system panicking as it is not expecting that kind of check to be reported.

The fix in this case is just to make the full check block also execute during an import operation. Note, that this behaviour matches the behaviour of other checkable objects. Resource pre and post conditions still execute during the validate operation, they just report warnings instead of errors. As check blocks already only report warnings, making all checkable objects consistent in this case is as simple as turning on check blocks during import.

Fixes #33572

Target Release

1.5.4

Draft CHANGELOG entry

BUG FIXES

• check blocks: Fixes crash when nested data sources are within configuration targeted by the terraform import command.
• check blocks: Check blocks now operate in line with other checkable objects by also executing during import operations.

[apparentlymart]

This sort of direct checking of the walk type does unfortunately tend to cause hazards like this under future maintenance. 😖

Hopefully in future we can find a more general way to solve this that doesn't require individually enumerating a specific subset of the walk types, but this seems like a good tactical fix for the immediate bug, and a good tradeoff for backporting.

[github-actions]

Reminder for the merging maintainer: if this is a user-visible change, please update the changelog on the appropriate release branch.

[github-actions]

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