[roll] Roll fuchsia [virtualization] Add vsock RX support for header only packets

This change adds RX support for control packets to be sent to the guest
(things like Request, Shutdown, CreditUpdate, etc). This uses a MPSC
model where each connection is a producer.

Control packets are sent on the first available RX chain. If there are
no pending control packets, the device will select! on both the control
packet endpoint and the connection socket.

See go/out-of-process-vsock-device for more information.

Original-Bug: 97355

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/687832
Original-Revision: 4ca5197b7c9415242903ee342adaae039bc9acf9
GitOrigin-RevId: fea2556744e9a992133292a2e93a45e7356b70af
Change-Id: I619be767c630d6687d45785cd60e58f2cc5edcd9

stem

diff --git a/stem b/stem
index cacb3a8..ab3f690 100644
--- a/stem
+++ b/stem
@@ -10,7 +10,7 @@
              githooks=""
              remote="https://fuchsia.googlesource.com/fuchsia"
              gerrithost="https://fuchsia-review.googlesource.com"
-             revision="685588685e60e9e85d72477baad86fe7c3411911"/>
+             revision="4ca5197b7c9415242903ee342adaae039bc9acf9"/>
   </projects>
   <hooks>
     <hook name="install-environment"