Serialization check -- only do one level

[mpharrigan]

The current automatic check for serialization is too slow to operate as a unit test or as part of the bloq_report_card notebook. We've been sprinkling in some skips but top-level bloqs will always be slow and always be sneaking in.

The check should just do one level of decomposition and serialization. The serializability of grand-callees of a bloq are not under the purview of the check/unit test for that bloq.

[tanujkhattar]

Also, if all bloqs have a serialization unit test, then chances are that grand callees are also serializable and therefore we can not have them as part of the unit test for every bloq