Bug: fix debugsystemui keybind

[pivotman319-owo]

What would this enhancement be for?

Tools

Describe your enhancement suggestion in more detail

DebugSystemUI was a tool Valve used to control rendering and AI behaviors in-game throughout Half-Life 2's development. The version that ships as part of HL2 relies on cvars that no longer exist in-engine or were renamed.

In Portal 2, this UI is effectively nonfunctional partly due to basemodui breaking input interactions and the fact that the resources for this feature (VGUI res files and debugoptions.txt) were removed at some point after Alien Swarm's release:

DebugSystemUI does not exist in Strata at all, even on legacyui mode. The keybind used to invoke it (Shift + F1) still exists but does nothing in its current state.

This issue merely suggests removing the bind.

[craftablescience]

We should hook this up to the existing imgui port of this window instead of removing it

[pivotman319-owo]

We should hook this up to the existing imgui port of this window instead of removing it

probably a better idea IMHO, could change it up to invoke devui_toggle_menu instead

[craftablescience]

It should probably work how fogui works