Use Slog instead of Log in UPS.

So that permission logs don't get flushed away when app logcat buffer
is full.

Slog is actually MODULE_LIBRARIES system API since ag/16823586.

Bug: 282984463
Test: presubmit
Change-Id: Id69a10a9d0c03145353fb96c1d0b31d34d1c9d0b