Correct test logic around SecureSettings#putStringForUser/putIntForUser

This changelist updates test code to mirror production code for how
settings values are stored and retrieved. Settings written as
int/string should only be read as int/string respectively.

Test: atest FontScalingDialogDelegateTest
Test: atest StickyKeysIndicatorViewModelTest
Flag: EXEMPT bugfix
Bug: 402551650
Change-Id: Ie3cb0c6a5f986fb9d62c08ee5477ce6a810c876e