runtime: add alignment info to sizeclasses.go comments
I was curious about the minimum possible alignment for each size class
and the minimum size to guarantee any particular alignment (e.g., to
know at what class size you can start assuming heap bits are byte- or
word-aligned).
Change-Id: I205b750286e8914986533c4f60712c420c3e63e9
Reviewed-on: https://go-review.googlesource.com/c/go/+/299909
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Michael Knyszek <mknyszek@google.com>
Trust: Matthew Dempsky <mdempsky@google.com>