tlsctx_client_session_cache_new() -> tlsctx_client_session_create()

tlsctx_client_session_cache_new() -> tlsctx_client_session_create()

Additionally to renaming, it changes the function definition so that
it accepts a pointer to pointer instead of returning a pointer to the
new object.

It is mostly done to make it in line with other functions in the
module.

(cherry picked from commit 7962e7f5757f77366bbcc4350ae43e5c0e4044c0)