fix(ime): flip the candidate position vertically if the bottom edge overflows bottom screen edge

[kenz-gelsoft]

Prepares to fix pop-os/cosmic-comp#2284 for COSMIC apps.

This depends on cosmic-comp PR:

• Fix IME popup positioning for Wayland input-method-v2 clients cosmic-comp#2320

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Basically pop-os/cosmic-comp#2320 fixes this but we specify the IME cursor rect to 0-height after #291 for workaround cosmic-comp issue, so flipping at screen bottom edge doesn't work correctly.

As pop-os/cosmic-comp#2320 will fix the root cause of #291, we can revert this once pop-os/cosmic-comp#2320 merged and released the cosmic-comp update to users.

1. before Fix IME popup positioning for Wayland input-method-v2 clients cosmic-comp#2320
   • it doesn't flip the popup direction at the bottom of the screen
     
2. after Fix IME popup positioning for Wayland input-method-v2 clients cosmic-comp#2320
   • it does flip vertically but doesn't respect the IME cursor area height.
   • this results in hiding the inputting text
     
3. after this PR
   • it filps and respect IME cursor height
     

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Revert "fix(ime): the candidate window position of fcitx5 which does't work well with winit's set_ime_cursor_area()"

Reverts #291