Handle secondary user

Use *AsUser variants of the APIs while adding intents to notification.
Right now, Warning activity doesn't show up for secondary user. This is
because activity is started for user when notification was posted
instead when it was clicked.

Test: m Settings && adb install -r $ANDROID_PRODUCT_OUT/system_ext/priv-app/Settings/Settings.apk
Test: Switch user and click notification
Bug: 405890417
Flag: EXEMPT bug_fix
Change-Id: I27dafbf21b7fe88ce3eb18d95df6c8e7803e7ca8