Add '-u <user id>' option to 'adb shell ime reset'

This is a preparation to add end-to-end CTS for per-profile IME mode.

In order to allow CTS tests to switch IME via shell command in
multi-user environment, this CL adds '-u <user id>' option to
  adb shell ime reset

Bug: 122924287
Test: Manually tested as follows:
  1. Build aosp_blueline-userdebug and flash it
  2. make -j SoftKeyboard
  3. adb install -r $OUT/system/app/SoftKeyboard/SoftKeyboard.apk
  4. adb shell ime enable com.example.android.softkeyboard/.SoftKeyboard
  5. adb shell ime set com.example.android.softkeyboard/.SoftKeyboard
  6. adb shell pm create-user test
  7. adb shell am switch-user 10
  8. adb shell ime list -s -u 0
     -> com.android.inputmethod.latin/.LatinIME
        com.example.android.softkeyboard/.SoftKeyboard
  9. adb shell ime reset -u 0
     -> Reset current and enabled IMEs for user #0
          Selected: com.android.inputmethod.latin/.LatinIME
           Enabled: com.android.inputmethod.latin/.LatinIME
 10. adb shell ime list -s -u 0
     -> com.android.inputmethod.latin/.LatinIME
Test: Manually tested as follows.
  1. Build aosp_blueline-userdebug and flash it
  2. adb shell pm create-user restricted_test
  3. adb root
  4. adb shell pm set-user-restriction --user 10 no_debugging_features 1
  5. adb shell ime reset -u all
     -> Reset current and enabled IMEs for user #0
          Selected: com.android.inputmethod.latin/.LatinIME
           Enabled: com.android.inputmethod.latin/.LatinIME
        User #10 is restricted with DISALLOW_DEBUGGING_FEATURES
Change-Id: Ie330c6faa76f366b78c15c0161873a051a3d40e3