use the same color for display name and fallback avatar

[HarHarLinks]

Is your suggestion related to a problem? Please describe.

Both colors are not user configurable (unless using an avatar image). From what I can tell, they're always different colors. This, in my mind, leads to a worse ability to make a mental link between both. Especially when searching the DM in room list, since it uses the avatar color.

Describe the solution you'd like.

For now, unify color generation algorithm.
In the long term I'd like to see user definable colors as part of global/space/room profiles.

Additional context

element-hq/element-meta#841

[t3chguy]

Related #2449 (comment)

[robintown]

So I tried this, and of course it looks good in the timeline, but it also starts to really change the look and feel of the room list, introducing a lot more visual noise:

(this example is showing rooms, but of course you get a similar rainbow effect for DMs without avatars)

[robintown]

Actually, this is a duplicate of #13490