Registers usearch and annoy properly via configure_config.cmake and
config.h.in like all other 3rd party libs, instead of (mis)using
target_compile_definitions.
No directory 'SimSIMD-map' exists, the build only worked because SimSIMD
support in usearch was (accidentally?) disabled. This commit corrects
the build description. SimSIMD support in usearch will be enabled by a
later commit.