Ignore onStartInput when WINDOW_FOCUS_GAIN_REPORT_WITH_SAME_EDITOR

CL[1] introduces new WINDOW_FOCUS_GAIN_REPORT_ONLY flows to notify
InputMethodService only reports IME input target to WM when focusing to
the next window and its input connection remains.

Originally in android Q and prior devices, we don't need such report
mechnism but just skip to start new input connection and ignore
onStartInput / onFinishInput for the above use case.

Since starts from Android R, new IME insets control APIs relying on this
mechanism (see CL[2]) to keep the actual IME input target up-to-date.

As we expected there should be no new input connection and additional
onFinishInput when CL[1] landed.

However, in IMMS, startInputUncheckedLocked will be called
to callback additional onStartInput for InputMethodService, which mostly
is not expected, except when focusing the same window after device
turned screen on, we need to start input and callback onStartInput to
align with the behavior of android Q or the prior platform.

Besides, to have more clear code logic and debugging concept of
ignoring onStartInput and onFinishInput only when focused the same editor
with input connection remains, we remove WINDOW_FOCUS_GAIN_REPORT_ONLY
reason and introduced 2 more start input reasons to distinguish the
different behavior:
    - WINDOW_FOCUS_GAIN_REPORT_WITH_SAME_EDITOR
    - WINDOW_FOCUS_GAIN_REPORT_WITHOUT_EDITOR

[1]: I45a9814d812ad906f417c24200fd4219959e2423
[2]: I9e8984b7e5aa989a53ece9e2576393f795b9ef94

Fix: 158624922
Test: atest FocusHandlingTest InputMethodStartInputLifecycleTest
Test: manual as below steps:
    1. Use Gboard, Open the emoji keyboard
    2. Swipe down to reveal notification shade
    3. Swipe up to dismiss notifications
    4. Expect the Emoji keyboard is still open without close

Change-Id: I2da99ae67b9ce4051dec0c0f0e975ebe6e1ab118