internal/poll: remove rsa field from Windows' poll.operation
The rsa field was added to the operation structure to avoid allocating
it every time it is needed. We can do better by using a sync.Pool to
reuse allocations across operations and FDs instead of the field.
A side benefit is that FD is now 16 bytes smaller and operation more
stateless.
Change-Id: I3b69a59e36b27f2cdd076cebd8d27a2a350b9c43
Reviewed-on: https://go-review.googlesource.com/c/go/+/698875 Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Damien Neil <dneil@google.com>