Fix single vs multi attach type issues in newer kernels

[gnurizen]

Fix ebpf attachment on newer kernels that don't allow cross attach
type tail call invocations.

Now we have to be consistent with the attach type we use for both the
main program and the tail call. We could just get rid of the multi
attach stuff but we'll eventually want it when we have hundreds of
programs we want to attach all over the place.

This broke with this kernel change:

commit 4540aed51b12bc13364149bf95f6ecef013197c0
Author: Daniel Borkmann <daniel@iogearbox.net>
Date:   Fri Sep 26 19:12:00 2025 +0200

bpf: Enforce expected_attach_type for tailcall compatibility

Yinhao et al. recently reported:

  Our fuzzer tool discovered an uninitialized pointer issue in the
  bpf_prog_test_run_xdp() function within the Linux kernel's BPF subsystem.
  This leads to a NULL pointer dereference when a BPF program attempts to
  deference the txq member of struct xdp_buff object.

...