CharacterMap: contrast too low for fallback characters

[humdinger]

This is hrev57820, 64bit.

The contrast is too low the fallback characters, i.e. those that are not part of the currently set font, but come from a fallback font:

It's also not playing well with a dark theme:

There's a patch at Gerrit to address this:

[humdinger]

old bright theme

[humdinger]

old dark theme

[humdinger]

This is the Gerrit path: ​https://review.haiku-os.org/c/haiku/+/7841

This is how it looks with those changes applied:

[humdinger]

new bright theme

[humdinger]

new dark theme

[waddlesplash]

Merged in hrev57825.