sched: programmable: Add user interface of task tag

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I8OIT1



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Add user interface of task tag, bridges the information
gap between user-mode and kernel mode.

Add proc interface:
  /proc/${pid}/task/${pid}/tag

Signed-off-by: Chen Hui <judy.chenhui@huawei.com>
Signed-off-by: Ren Zhijie <renzhijie2@huawei.com>
Signed-off-by: Hui Tang <tanghui20@huawei.com>
Signed-off-by: Guan Jing <guanjing6@huawei.com>