selftests/bpf: add demo for file read pattern detection

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4H3JT


CVE: NA

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It attaches eBPF program into fs_file_read() and fs_file_release()
respectively. The program for fs_file_read() will record read
history, calculate read pattern and set f_mode for specific file,
And program for fs_file_release() will clean the saved read history.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Reviewed-by: Kuohai Xu <xukuohai@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>