Merge branch 'bpf-add-bitwise-tracking-for-bpf_end'

Tianci Cao says:

====================
bpf: Add bitwise tracking for BPF_END

Add bitwise tracking (tnum analysis) for BPF_END (`bswap(16|32|64)`,
`be(16|32|64)`, `le(16|32|64)`) operations. Please see commit log of
1/2 for more details.

v3:
- Resend to fix a version control error in v2.
- The rest of the changes are identical to v2.

v2 (incorrect): https://lore.kernel.org/bpf/20260204091146.52447-1-ziye@zju.edu.cn/
- Refactored selftests using BSWAP_RANGE_TEST macro to eliminate code
  duplication and improve maintainability. (Eduard)
- Simplified test names. (Eduard)
- Reduced excessive comments in test cases. (Eduard)
- Added more comments to explain BPF_END's special handling of zext_32_to_64.

v1: https://lore.kernel.org/bpf/20260202133536.66207-1-ziye@zju.edu.cn/
====================

Link: https://patch.msgid.link/20260204111503.77871-1-ziye@zju.edu.cn
Signed-off-by: Alexei Starovoitov <ast@kernel.org>