selftests/bpf: Factor out many args tests from tracing_struct

Factor out many args tests from tracing_struct and rename some function names
to make more sense. Meanwhile, remove unnecessary skeleton detach operation
as it will be covered by skeleton destroy operation.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Link: https://lore.kernel.org/bpf/20240702121944.1091530-3-pulehui@huaweicloud.com