Don't use mid/average TC color for UI elements

Describe the desired feature

Team color is applied to the magenta pixels of the unit sprites, and we can adjust the max(), mid(), and min() colors with specific values to find a good range that maps to the sprites. To make the team colors easier to distinguish on the minimap, there is a fourth color specified in data/core/team-colors.cfg.

For the sprite ellipse, the range mid() value is mapped to the red pixels of the ellipse images (RC IPF). I didn't look into it as much, but something similar is done with the player names in the MP chat text.

The mid() value, or at least the range, must look good on the sprites, be legible against the dark chat background, and be visible against all terrains. This is asking too much. The ellipses and the font color should be separate from the sprite recolor, just like the minimap is. Maybe the minimap value can be used for ellipses & text, or maybe we need two new additional values defined for each color.

An example is the "black" team color - it can be gray, where the sprite TC isn't really "black" but at least it doesn't have any other colors, the ellipse is an irrelevant gray smudge, and the font is sort of visible in chat. Or we can make the range darker, so that the sprite is more "black", the ellipse is visible (on most terrain), and the chat text is invisible.

This is related to #11492