lib: make public reference count functions have strict types

lib: make public reference count functions have strict types

Instead of having generic bt_object_get_ref() and bt_object_put_ref()
accepting `const void *`, have one pair of such functions for each
shared object API.

This can help catch reference count bugs (not putting or getting the
correct object type) and makes it illegal at build time to get or put a
unique object's reference.

Each shared object API also has its own BT_X_PUT_REF_AND_RESET() and
BT_X_MOVE_REF() macros.

bt_object_get_ref() and bt_object_put_ref() are now internal and only
used by the library's implementation.

Signed-off-by: Philippe Proulx <eeppeliteloop@gmail.com>