Fixed initial mDisplayId on KeyEvent.

Some constructors were explicitly setting it to INVALID_DISPLAY,
while others wouldn't (and in those cases mDisplayId would be 0,
which is DEFAULT_DISPLAY), which made it harder to change the
display id for tests running on background users visible on
secondary displays.

Test: atest KeyEventTest CtsAppTestCases:android.app.cts.LauncherActivityTest
Bug: 266851112
Fixes: 268103680

Change-Id: I9ee61784109620f7b505d8b8db479b37b9a42e20