selftests/bpf: Handle batch operations for map-in-map bpf-maps

This patch adds up test cases that handles 4 combinations:
 a) outer map: BPF_MAP_TYPE_ARRAY_OF_MAPS
    inner maps: BPF_MAP_TYPE_ARRAY and BPF_MAP_TYPE_HASH
 b) outer map: BPF_MAP_TYPE_HASH_OF_MAPS
    inner maps: BPF_MAP_TYPE_ARRAY and BPF_MAP_TYPE_HASH

Signed-off-by: Takshak Chahande <ctakshak@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20220510082221.2390540-2-ctakshak@fb.com