design: regenerate graphs for GC pacer redesign

A couple of the graphs were wrong (from the wrong scenario, that is)
because I copied them in manually. Fatal mistake.

Regenerate the graphs following the usual pipeline. Because there's
a degree of jitter and randomness in these graphs they end up slightly
different, but they're all mostly the same.

By regenerating these graphs, it also adds a new line to each graph
for the live heap size. I think this is nice for readability, so I'll
let that get updated too.

For golang/go#44167.

Change-Id: I097f812ba07ca7fd740d8460e2830de6492b3945
Reviewed-on: https://go-review.googlesource.com/c/proposal/+/293790
Reviewed-by: Michael Pratt <[email protected]>

Author: mknyszek