Retire testing utils `get_frame_by_name()`

[scotts]

We have some Python-based tests that predate the current testing framework. The testing framework has the API call get_frame_by_name() implemented to support instances where we were testing against a reference frame and we didn't know its index.

In general, all of our Python tests should test against frames whose index we know, and we should refer to it through the APIs in our testing framework. Retiring get_frame_by_name() will required converting the existing tests to refer to the frame by index, and updating the metadata for the frame and potentially the name of the frame itself to match.