Whitepaper: Consider "promoting" Continuous Profiling to primary observability signals.

[bwplotka]

Suggestion from our final 1.0 community review period by @nicolastakashi.

It might be indeed time to promote Continuous Profiling to main "three pillars" (which we renamed to primary signals). Not sure what are benefit of that or when we do this. Also how to draw those 3 circles we have in Figure 1 (:

Perhaps worth to discuss it!