Add getInputMethodList API for locked user state

When work profile disable by quick settings, the
user would be locked then we cannot query installed
input method lists for work user by existings API
InputMethodManager#getInputMethodListAsUser().

Adding a new API to query input method services
regardless of the user state. This API currently
only used by Settings, it shouldn't affect the
original behavior for other usages.

Bug: 210083408
Test: verify we can get input methods list after
      disable work apps by quick settings
Test: atest CtsInputMethodTestCases
Change-Id: I54d5dbec7e76d6a68935007ed3af0641f717a7c5