Colors: Support unique color by value across fields

### Discussed in https://github.com/grafana/grafana/discussions/38306 <div type='discussions-op-text'> ^{Originally posted by **colega** June 18, 2021} <!-- Please only use this template for submitting feature requests --> **What would you like to be added**: a "Classic palette" which has colors assigned by value, like in [other color schemes](https://user-images.githubusercontent.com/1511481/122519491-cfd89b00-d012-11eb-93ae-3774fc38c4c0.png). Or, even better, assigning \[pseudo-\]unique values to each new value in the series [instead of value percentage-based](http://github.com/grafana/grafana/blob/7f882eea05d7054407cf2c1fa05cbfe38414aa05/packages/grafana-data/src/field/fieldColor.ts#L195-L195). **Why is this needed**: in the new _State timeline_ panel introduced in Grafana 8, choosing the palettes that assign colors by value makes more sense than selecting different colors for different series, since it allows us to visually differentiate the values. Consider the difference between this panel representing a version history:  And this one:  The latter one is not perfect, but at least it's _visually more distinguishable_. It represents some issues however: - The value in the middle gets assigned the last color, so we can't really see that there are three values there (three text labels are the only clue, I actually [opened a bug report for this first](https://github.com/grafana/grafana/issues/35934), since I thought it was the same color, but it's just very similar). - Regardless the _color scheme "by value"_ we choose, it adds a semantic to the value (in this case value is a timestamp, but newer doesn't mean it's better or worse, it's just a different value) As a proof of concept, I tried this (this is my first contact with TypeScript :D)…