selftests/bpf: Add BTF dedup tests for recursive typedef definitions

selftests/bpf: Add BTF dedup tests for recursive typedef definitions

Add several ./test_progs tests:
    1.  btf/dedup:recursive typedef ensures that deduplication no
	longer fails on recursive typedefs.
    2.  btf/dedup:typedef ensures that typedefs are deduplicated correctly
	just as they were before this patch.

Signed-off-by: Paul Houssel <paul.houssel@orange.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/9fac2f744089f6090257d4c881914b79f6cd6c6a.1763037045.git.paul.houssel@orange.com