selftests/bpf: Call bpf_get_numa_node_id() in trigger_count()

selftests/bpf: Call bpf_get_numa_node_id() in trigger_count()

The bench test "trig-kernel-count" can be used as a baseline comparison
for fentry and other benchmarks, and the calling to bpf_get_numa_node_id()
should be considered as composition of the baseline. So, let's call it in
trigger_count(). Meanwhile, rename trigger_count() to
trigger_kernel_count() to make it easier understand.

Signed-off-by: Menglong Dong <dongml2@chinatelecom.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20251116014242.151110-1-dongml2@chinatelecom.cn