Plan out testing clang internal features with new Checked C features

[secure-sw-dev-bot]

This issue was copied from checkedc/checkedc-clang#10

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We need to test printing, AST serialization, AST transformation, and AST serialization with the new Checked C features. This work item is to understand the tests that exist for these features and how to extend them to Checked C features.

[secure-sw-dev-bot]

Comment from @dtarditi:

No need to have a separate planning work item for this. We have issues open for the features that remain to be tested better. Closing this issue.