Use user-aware context when calling getImeAndSubtypeDisplayName

Ensure we get the corresponding PackageManager instance from the user
context to load the text resources of the IME package and the subType.

Fix: 223418203
Test: manual as steps
    0) Pair a physical keyboard or use
       "adb shell setprop qemu.hw.mainkeys 1` to disable navigation bar
    0-1) Restart device with "adb shell am restart"
    0-2) After the system restarted, add a new user from Settings >
         System > Multiple users
    0-3) Switch to the new user to setup and install some IME apps.
    1) Switch to the owner user from Status bar -> Select user icon
    2) Tap the editor from the google search box to show soft-keyboard
    3) After the soft-keyboard displayed, verify "Choose input method"
       notification has popuped on the notification shade, and check
       the current IME subType display name & the IME package label
       are displyed correctly.
    4) Repeat step 1-3 for the new user again.

Change-Id: I58421143bee25be459f4f744688b37614a750051