ImGuiIntegration: don't use obsolete enum aliases

[sthalik]

This is useful to me because clangd chokes on the oversized ImGui header and reducing its size through IMGUI_DISABLE_OBSOLETE_FUNCTIONS helps a bit.

[pezcode]

This would break for anyone using 1.87 and 1.88, since those enums only got renamed in 1.89 WIP: https://github.com/ocornut/imgui/commit/fd408c97904fbf9f3b4c786318e8389de11bc681

Best solution I can think of is to use the new enums optionally behind #if IMGUI_VERSION_NUM >= 18823. Might be a bit messy, but supporting IMGUI_DISABLE_OBSOLETE_FUNCTIONS is indeed valuable.

[codecov[bot]]

Codecov Report

Base: 76.67% // Head: 76.67% // No change to project coverage :thumbsup:

Coverage data is based on head (6ad015e) compared to base (a4f3278). Patch has no changes to coverable lines.

Additional details and impacted files

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[mosra]

Thanks!