rtld: add a test for RTLD_DEEPBIND

This tests that with RTLD_DEEPBIND, symbols are looked up in all of the
object's needed objects before the global object.

PR: 275393
Reviewed by: kib
Sponsored by: NetApp, Inc.
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D42843