don't trickle fast imgui inputs

[nornagon]

Summary

Bugfixes "Fixed frame lag in imgui text inputs"

Purpose of change

Fixed laggy text input in imgui windows.

See #73052. This fixes the issue on macOS. The issue might be the same on
Android (and thus also fixed by this change), but I haven't verified.

Describe the solution

There's an imgui feature that's supposed to prevent "skipping" inputs that
happen quickly by trickling them out one per frame if they happen on the same
key. However, this seems to also be applying to the "keydown" event and then
the "text" event, which both "involve" the same key, even though they're just
two different views of the same event.

This could plausibly be described as an ImGui bug—the trickling behavior could
be useful for repeated down/up/down sequences on a key, perhaps, but it
shouldn't apply to text events—but I'm not sure we really want the trickling
behavior at all, so this patch just disables it.

Describe alternatives you've considered

Testing

Additional context

[katemonster33]

I can't verify whether the Android issue is fixed by this branch as my phone appears unaffected - I have pulled the commit to my master branch and created an experimental Android build, it can be found here https://github.com/katemonster33/Cataclysm-DDA/releases/tag/cdda-experimental-2024-04-22-0254 anyone with an Android device affected by #73052 should give this a try

Anyway, I tested this on Windows, did not notice any regressions on the keybindings UI.