[Fix settings] Multi user for settings wrapper

Audit and fix SettingsProxy usages to account for multiple users.

Note that this does not fix any Settings usages that does not use
SettingsProxy. There maybe be outstanding files to change, but from a
glance, most of the usages seem to be user aware.

Bug: 226391543
Test: Manual and fixed unit tests

Change-Id: Ia8ff59fe55049cc79ac73237087d3aaca2cbb3b3