Add IME event intent, receiver, and content provider

The Java classes in android.inputmethodservices.cts.common package
define String constants which are relevant for both device-side and
host-side.

Bug: 7542467
Test: Installing CtsInputMethodServiceEventProvider.apk and confirming that
      content provider can handle insert request by
        adb install -r CtsInputMethodServiceEventProvider.apk
        adb shell content insert --uri content://android.inputmethodservice.cts.provider/events \
          --bind sender:s:sender1 --bind type:s:TEST_START --bind time:l:1234
Test: After the above test, confirming that content provider can
      handle query request by
        adb shell content query --uri content://android.inputmethodservice.cts.provider/events
      and confirming the result is
        Row: 0 _id=1, sender=sender1, type=TEST_START, time=1234
Change-Id: I9aa37a7237d9f7a4504d702473b599bd4f2c94ec
11 files changed