pixelstats: move learning/model load path to sysfs

Reporting learning(relaxation) and model loading once a day
 * learning and model loading path moved from uevent to
   sysfs collector.

Bug: 329124192
Signed-off-by: Chungro Lee <chungro@google.com>
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:5dc71cfae1304564ccb2861109e9e1451032f0e7)
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:0d11a6641db189497e94b383fd4de86b9e50d529)
Merged-In: I91039ce3a8ee4630a76113ef7ae6be3bc6908f64
Change-Id: I91039ce3a8ee4630a76113ef7ae6be3bc6908f64