selftests/bpf: add extra test for using dynptr data slice after release

selftests/bpf: add extra test for using dynptr data slice after release

Add an additional test, "data_slice_use_after_release2", for ensuring
that data slices are correctly invalidated by the verifier after the
dynptr whose ref obj id they track is released. In particular, this
tests data slice invalidation for dynptrs located at a non-zero offset
from the frame pointer.

Signed-off-by: Joanne Koong <joannelkoong@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220809214055.4050604-2-joannelkoong@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>