* other: group all dataset draws in a time chart
We used to draw each data set separately as a new canvas. Now, in one
canvas, we draw all datasets.
Note that this changes how dataset lines are drawn - rather than
drawing one on top of another, it now draws kinda all at once. This
effect is *kinda* a bit better IMO, but it might also look a bit
more cluttered.
* other: optimize truncate_text
Flamegraphs showed that this area seems to be a bit heavy at times with
some inefficient use of iterators and collection. This change should
hopefully optimize this a bit by reducing some collections or
reallocations.
There can also be some further optimizations with less allocations from
callers.
* Reduce some redundant draws
9c3e60e74f