tools/vm/page_owner_sort.c: support for multi-value selection in single argument

tools/vm/page_owner_sort.c: support for multi-value selection in single argument

When viewing page owner information, we may want to select blocks whose
PID/TGID/TASK_COMM_NAME appears in a user-specified list for data analysis
and aggregation.  But currently page_owner_sort only supports selecting
blocks associated with only one specified PID/TGID/TASK_COMM_NAME.

Therefore, following adjustments are made to fix the problem:

1. Enhance selecting function to support the selection of multiple
   PIDs/TGIDs/TASK_COMM_NAMEs.

The enhanced usages are as follows:

--pid <pidlist>         Select by pid. This selects the blocks whose PID
                        numbers appear in <pidlist>.
--tgid <tgidlist>       Select by tgid. This selects the blocks whose
                        TGID numbers appear in <tgidlist>.
--name <cmdlist>        Select by task command name. This selects the
                        blocks whose task command name appear in <cmdlist>.

Where <pidlist>, <tgidlist>, <cmdlist> are single arguments in the form of
a comma-separated list,which offers a way to specify individual selecting
rules.

For example, if you want to select blocks whose tgids are 1, 2 or 3, you
have to use 4 commands as follows:

        ./page_owner_sort <input> <output1> --tgid=1
        ./page_owner_sort <input> <output2> --tgid=2
        ./page_owner_sort <input> <output3> --tgid=3
        cat <output1> <output2> <output3> > <output>

With this patch, you can use only 1 command to obtain the same result as
above:

        ./page_owner_sort <input> <output1> --tgid=1,2,3

2. Update explanations of --pid, --tgid and --name in the function
   usage() and the document(Documents/vm/page_owner.rst).

This work is coauthored by
        Yixuan Cao
        Shenghong Han
        Yinan Zhang
        Chongxi Zhao
        Yuhong Feng
        Yongqiang Liu

Link: https://lkml.kernel.org/r/20220401024856.767-2-yejiajian2018@email.szu.edu.cn
Signed-off-by: Jiajian Ye <yejiajian2018@email.szu.edu.cn>
Cc: Chongxi Zhao <zhaochongxi2019@email.szu.edu.cn>
Cc: Shenghong Han <hanshenghong2019@email.szu.edu.cn>
Cc: Yinan Zhang <zhangyinan2019@email.szu.edu.cn>
Cc: Yixuan Cao <caoyixuan2019@email.szu.edu.cn>
Cc: Yongqiang Liu <liuyongqiang13@huawei.com>
Cc: Yuhong Feng <yuhongf@szu.edu.cn>
Cc: Haowen Bai <baihaowen@meizu.com>
Cc: Sean Anderson <seanga2@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>