bpf: Add bpf_guard_preempt() convenience macro

Add bpf_guard_preempt() macro that uses newly introduced
bpf_preempt_disable/enable() kfuncs to guard a critical section.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20240424225529.16782-1-alexei.starovoitov@gmail.com


Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>