[netdevice] Add eventpair variant to DelegatedRxLease

Add support for `zx.Handle:EVENT`-based event tokens to
`DelegatedRxLease`. This allows `DelegatedRxLease` to hold the latest
format of `LeaseToken` provided by the system `ActivityGovernor`.

Bug: 466406261
Test: fx lsc presubmit

Change-Id: I32b0a8bb499e6035636617e84e72a1174c709c1e
Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/1441103
API-Review: Bruno Dal Bo <brunodalbo@google.com>
Reviewed-by: Bruno Dal Bo <brunodalbo@google.com>
Commit-Queue: Eric Rahm <erahm@google.com>

Author: EricRahm

sdk/fidl/fuchsia.hardware.network/fuchsia.hardware.network.api

@@ -1,3 +1,3 @@
 {
-  "fidl/fuchsia.hardware.network": "a9e6cec0381f284a40084b7c21743ee5"
+  "fidl/fuchsia.hardware.network": "81341dd7df98ad5985dfc6f4cdde4a35"
 }

sdk/fidl/fuchsia.hardware.network/session.fidl

@@ -204,5 +204,10 @@ type DelegatedRxLease = resource table {
         ///
         /// Close the channel to release the lease.
         1: channel zx.Handle:CHANNEL;
+        /// An eventpair representing a lease.
+        ///
+        /// Close the eventpair to release the lease.
+        2: eventpair
+                zx.Handle:<EVENTPAIR, zx.Rights.TRANSFER | zx.Rights.DUPLICATE | zx.Rights.WAIT>;
     };
 };

src/connectivity/lib/network-device/rust/src/session/mod.rs

@@ -801,6 +801,9 @@ impl Drop for RxLease {
             netdev::DelegatedRxLeaseHandle::Channel(_channel) => {
                 // Dropping the channel is enough to relinquish the lease.
             }
+            netdev::DelegatedRxLeaseHandle::Eventpair(_eventpair) => {
+                // Dropping the eventpair is enough to relinquish the lease.
+            }
             netdev::DelegatedRxLeaseHandle::__SourceBreaking { .. } => {}
         }
     }

src/connectivity/network/drivers/network-device/device/device_interface.cc

@@ -1479,6 +1479,7 @@ void DeviceInterface::DropDelegatedRxLease(netdev::DelegatedRxLease lease) {
   // simply destroying the natural type is not enough to drop the lease.
   switch (lease.handle()->Which()) {
     case netdev::DelegatedRxLeaseHandle::Tag::kChannel:
+    case netdev::DelegatedRxLeaseHandle::Tag::kEventpair:
     case netdev::DelegatedRxLeaseHandle::Tag::_do_not_handle_this__write_a_default_case_instead:
       break;
   }