pixel_stats: add access to PSI information

Add access to PSI information, i.e. /proc/pressure/xyz,
where xyz=cpu, io, or memory.

Test: local test
Bug: 233841658
Signed-off-by: Robin Hsu <robinhsu@google.com>
Change-Id: Ic433cd2ebfdd24694ed63bee118e30e286c11b41
1 file changed