core: generic buffer inside/outside/intersect routine

Remove multiple implementation of "is buffer inside a buffer" and
friends and rely on a generic core_is_buffer_inside/outside/intersect().

Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Tested-by: Pascal Brand <pascal.brand@linaro.org> (STM platform)
Signed-off-by: Pascal Brand <pascal.brand@st.com>