m/pkg/event: move MemoryValue to subpackage

This keeps metropolis/pkg/event as a pure interface package, and
moves the memory-backed implementation to a subpackage.

Test Plan: Refactor, coevered by tests.

X-Origin-Diff: phab/D764
GitOrigin-RevId: 1337bf55a7752293791b3efe8648bbf5f6e6e9e1
diff --git a/metropolis/node/core/cluster/BUILD.bazel b/metropolis/node/core/cluster/BUILD.bazel
index a3e2593..948b9ae 100644
--- a/metropolis/node/core/cluster/BUILD.bazel
+++ b/metropolis/node/core/cluster/BUILD.bazel
@@ -17,6 +17,7 @@
         "//metropolis/node/core/localstorage:go_default_library",
         "//metropolis/node/core/network:go_default_library",
         "//metropolis/pkg/event:go_default_library",
+        "//metropolis/pkg/event/memory:go_default_library",
         "//metropolis/pkg/pki:go_default_library",
         "//metropolis/pkg/supervisor:go_default_library",
         "//metropolis/proto/api:go_default_library",
diff --git a/metropolis/node/core/cluster/manager.go b/metropolis/node/core/cluster/manager.go
index 874d3ae..eede40f 100644
--- a/metropolis/node/core/cluster/manager.go
+++ b/metropolis/node/core/cluster/manager.go
@@ -30,6 +30,7 @@
 	"source.monogon.dev/metropolis/node/core/localstorage"
 	"source.monogon.dev/metropolis/node/core/network"
 	"source.monogon.dev/metropolis/pkg/event"
+	"source.monogon.dev/metropolis/pkg/event/memory"
 	"source.monogon.dev/metropolis/pkg/supervisor"
 	apb "source.monogon.dev/metropolis/proto/api"
 	ppb "source.monogon.dev/metropolis/proto/private"
@@ -132,7 +133,7 @@
 type Manager struct {
 	storageRoot    *localstorage.Root
 	networkService *network.Service
-	status         event.MemoryValue
+	status         memory.Value
 
 	state
 
diff --git a/metropolis/node/core/network/BUILD.bazel b/metropolis/node/core/network/BUILD.bazel
index 10378c1..489f1d4 100644
--- a/metropolis/node/core/network/BUILD.bazel
+++ b/metropolis/node/core/network/BUILD.bazel
@@ -10,6 +10,7 @@
         "//metropolis/node/core/network/dhcp4c/callback:go_default_library",
         "//metropolis/node/core/network/dns:go_default_library",
         "//metropolis/pkg/event:go_default_library",
+        "//metropolis/pkg/event/memory:go_default_library",
         "//metropolis/pkg/supervisor:go_default_library",
         "@com_github_google_nftables//:go_default_library",
         "@com_github_google_nftables//expr:go_default_library",
diff --git a/metropolis/node/core/network/main.go b/metropolis/node/core/network/main.go
index 9284b30..49ace2e 100644
--- a/metropolis/node/core/network/main.go
+++ b/metropolis/node/core/network/main.go
@@ -33,6 +33,7 @@
 	dhcpcb "source.monogon.dev/metropolis/node/core/network/dhcp4c/callback"
 	"source.monogon.dev/metropolis/node/core/network/dns"
 	"source.monogon.dev/metropolis/pkg/event"
+	"source.monogon.dev/metropolis/pkg/event/memory"
 	"source.monogon.dev/metropolis/pkg/supervisor"
 )
 
@@ -53,7 +54,7 @@
 	natTable            *nftables.Table
 	natPostroutingChain *nftables.Chain
 
-	status event.MemoryValue
+	status memory.Value
 }
 
 func New() *Service {