selftests/bpf: add tests confirming type logic in kernel for __arg_ctx

selftests/bpf: add tests confirming type logic in kernel for __arg_ctx

Add a bunch of global subprogs across variety of program types to
validate expected kernel type enforcement logic for __arg_ctx arguments.

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20240118033143.3384355-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>