Merge branch 'selftests-xsk-add-tests-for-xdp-tail-adjustment-in-af_xdp'

Tushar Vyavahare says:

====================
selftests/xsk: Add tests for XDP tail adjustment in AF_XDP

This patch series adds tests to validate the XDP tail adjustment
functionality, focusing on its use within the AF_XDP context. The tests
verify dynamic packet size manipulation using the bpf_xdp_adjust_tail()
helper function, covering both single and multi-buffer scenarios.

v1 -> v2:
1. Retain and extend stream replacement: Keep `pkt_stream_replace`
   unchanged. Add `pkt_stream_replace_ifobject` for targeted ifobject
   handling.

2. Consolidate patches: Merge patches 2 to 6 for tail adjustment tests and
   check.

v2 -> v3:
1. Introduce `adjust_value` to replace `count` for clearer communication
   with userspace.

v3 -> v4:
1. Remove `testapp_adjust_tail_common()`. [Maciej]

2. Add comments and modify code for buffer resizing logic in test cases
   (shrink/grow by specific byte sizes for testing purposes). [Maciej]
====================

Link: https://patch.msgid.link/20250410033116.173617-1-tushar.vyavahare@intel.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>