before this, Milvus use container/system's memory info to get the memory
usage, which could be inaccurate.
we allocates the memory by private anon mmap,
then rss - shared would be the accurate memory usage
resolve https://github.com/milvus-io/milvus/issues/28553
pr: #28554
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Signed-off-by: yah01 <yah2er0ne@outlook.com>
Signed-off-by: yah01 <yang.cen@zilliz.com>