selftests/bpf: add more variations of map-in-map situations

Add test cases validating usage of PERCPU_ARRAY and PERCPU_HASH maps as
inner maps.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20240515062440.846086-2-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>