Perf: Make scatter point color computation faster

[themadcreator]

• Update scatter plot example with varies colors
• Add high-scale canvas bar plot example
• Previously, color computations in the inner render loop were making many calls to .domain() and .range(). These have negative impact on performance, so instead we carefully cache the relevant information instead of constantly recomputing it.

[blueprint-bot]

Perf: Make scatter point color computation faster

Demo: quicktests | fiddle