selftests/bpf: Align kfuncs renamed in bpf tree

selftests/bpf: Align kfuncs renamed in bpf tree

bpf_task_work_schedule_resume() and bpf_task_work_schedule_signal() have
been renamed in bpf tree to bpf_task_work_schedule_resume_impl() and
bpf_task_work_schedule_signal_impl() accordingly.
There are few uses of these kfuncs in selftests that are not in bpf
tree, so that when we port [1] into bpf-next, those BPF programs will
not compile.
This patch aligns those remaining callsites with the kfunc renaming.
It should go on top of [1] when applying on bpf-next.

1: https://lore.kernel.org/all/20251104-implv2-v3-0-4772b9ae0e06@meta.com/

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Link: https://lore.kernel.org/r/20251105132105.597344-1-mykyta.yatsenko5@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>