Merge branch 'bpftool-selftests-add-tests-for-c-dump-and-fix-a-dropped-type'

Ihor Solodrai says:

====================
bpftool, selftests: Add tests for C dump and fix a dropped type

"bpftool btf dump format c" generates the vmlinux.h that BPF programs
are built against, and it has no direct test coverage. Building
against the header is not a substitute for testing it, nothing a
compiler accepts would break the build.

Add selftests targeting C dump in particular.

While we are here, refactor btf_dump selftests to use a new
compare_text_to_expected() helper and become more efficient.

Fix a bug in bpftool dump that dropped a type when sorting.
---

v1->v2:
  * new patches (#1-#3) introducing compare_text_to_expected() helper
    and refactoring btf_dump selftests
  * bpftool dump selftest compares the output to the expected files
    exactly (Eduard)
  * use VALIDATE_RAW_BTF macro in the new test (Eduard)
  * drop v1 patch #4 ("selftests/bpf: Check that sorting preserves
    types in bpftool dump") as it became unnecessary
  * nit in the bpftool fix (Andrii)

v1: https://lore.kernel.org/bpf/20260820000627.3826188-1-ihor.solodrai@linux.dev/
====================

Link: https://patch.msgid.link/20260828215207.3105313-1-ihor.solodrai@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>