Change Boyer Moore search API for take BmCtx

Change the API for BoyerMoore to take a BmCtx rather than the two parts that
are stored in the context. Which is how it is mostly used. This enforces
always calling BoyerMooreCtxToNocase() to convert to no-case.

Use CtxInit and CtxDeinit functions to create and destroy the context,
even in unit tests.