Merge branch 'sev/hud_kh' into 'master'

Merge branch 'sev/hud_kh' into 'master'

Reimplemented Keyhunt HUD modicon panel

The current Keyhunt HUD modicon panel is overly complicated and inconsistent with other gametypes:

- It uses most of the available space to show the original key color, which is irrelevant for the gameplay
- Teams are not grouped
- Ownership is conveyed with different alpha values, which is difficult to understand
- As a result, you get an "RGBA salad"

This branch reimplements the panel:

- Each key is shown in the color of its current owning team
- Keys are grouped by team
- The icons use the same taken/carrying/dropped pattern used for CTF
- The icons blink if RUN HERE is shown
- The icons are more evenly distributed in the available space, esp. in the case of fewer than 4 teams

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![kh](https://gitlab.com/uploads/xonotic/xonotic-data.pk3dir/b8cb9585fd/kh.png)

See merge request !75