mm: compaction: refactor compact_node()

Refactor compact_node() to handle both proactive and synchronous compact
memory, which cleanups code a bit.

Link: https://lkml.kernel.org/r/20240208013607.1731817-1-wangkefeng.wang@huawei.com


Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>