runtime: use eventfd as the event wait/notify mechanism for epoll

runtime: use eventfd as the event wait/notify mechanism for epoll

Fixes #65443

Change-Id: I9ad4689b36e87ee930d35a38322a8797896483b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/560615
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Than McIntosh <thanm@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>