Fix IME window can't show on Simulated display

CL Icfd66689dad4b782c50b56a515194dd138d3b280 introduced
WindowManagerInternal#shouldShowIme for IMMS to check if the display can
show IME window, which just calling DisplayWindowSettings#shouldShowIme.

That will missed Simulated display use case & we should use WMS#shouldShowIme
since we have already implemented force desktop mode check for simulated
display with combined DisplayWindowSettings#shouldShowIme in above CL.

Correct the API usage to fix the issue.

Fix: 131921175
Fix: 129443632

Test: atest MultiDisplaySystemDecorationTests
Test: atest DisplayWindowSettingsTests#testShouldShowImeWithinForceDesktopMode
Test: manual as below steps:
 1. adb shell settings put global force_desktop_mode_on_external_displays 1
 2. adb shell settings put global overlay_display_devices 1080x1920/320
 3. adb reboot, make sure simulated display overlaid on device.
 4. By using a Bluetooth mouse or a USB mouse, launch any Activity on
    simulated display that has an input field.
 5. Click that input field to see if IME window can shown simulated display.

Change-Id: I5b592f7152dffb12826c6cbd8ab466fcf1392fb7