selftests/bpf: Verify inlined numeric iterator shape with __xlated

Add an __xlated test pinning the inlined bpf_iter_num_{new,next,destroy}()
shapes. The program is __naked, so there is no compiler glue and the whole
sequence is matched instruction for instruction.

Gate it to x86_64 and arm64 (bpf_jit_needs_zext() == false); elsewhere the
verifier interleaves "wN = wN" zero-extensions that would not match. The
inlining is arch independent, so these two are enough.

Suggested-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260804134601.2305303-6-puranjay@kernel.org