runtime: ensure at least 1 tick between events

runtime: ensure at least 1 tick between events

ticks might be same after tick division, although the real cputicks
is linear growth

Fixes #46737

Change-Id: I1d98866fbf21b426c6c1c96cc9cf802d7f440f18
Reviewed-on: https://go-review.googlesource.com/c/go/+/330849
Trust: Meng Zhuo <mzh@golangcn.org>
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Meng Zhuo <mzh@golangcn.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>