Add API for checking whether the default IME was set by the DO/PO

With this API, the system can determine whether a user's default
IME was set by the user or the user's DO/PO.

Bug: 32692748
Test: DPMS unit tests and CTS CtsDevicePolicyManagerTestCases

Change-Id: Ibd703ff5c9e4c072599ad8d6023c94a97d728109
7 files changed