add cmp_thunk function to ossl_bsearch

add cmp_thunk function to ossl_bsearch

Add the initial groundwork to allow for the use of a thunking function
with bsearch.  Normally our comparison function signature doesn't match
the type of the pointer we call it through, leading to ubsan errors,
this lets those signatures match and gives us a place to do the proper
casting

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Nikola Pajkovsky <nikolap@openssl.org>
MergeDate: Sat Feb  7 18:11:11 2026
(Merged from https://github.com/openssl/openssl/pull/29640)