Generate OOB data Topshim API

This implements the topshim portion and testing API for calling in to
generate local out of band data.

Bug: 234756905
Test: system/gd/cert/run --clean --topshim LeSecurityTest.test_generate_local_oob_data
Tag: #floss
Change-Id: Ia056238fc77fb12e60dca17fba41dc6a184b6181