Test framework does not call Bap_main.init

It is technically "undefined behavior" to call any BAP function without first having called Bap_main.init to load a number of things, including Lisp semantics and disassemblers.

We either need to publish a run_unit : unit -> unit in the lib and call it in the plugin, or do something akin to here: https://github.com/BinaryAnalysisPlatform/bap/blob/master/lib_test/bap/run_tests.ml