core: sausage-vfs per process (/, /proc, /self, /run), activation, graph, watcher, upgrades

- /proc is a core layer: core/ (PROTOCOL.md, graph.json, graph.dot,
  locks.json, plugins/<name>/discover.json and client.rs) and one folder
  per process (info.json, log, and its /self files).
- Locks are released only after the task ended, the store dropped, and
  in-flight file operations returned.
- core.activate and core.revert with copies, discovery, compatibility
  checks of imports and consumers, groups, force. An admission gate
  makes the snapshot of old processes complete.
- Graph of discover documents by hash, refreshed by a file watcher.
- Upgrades: grace periods (x-sausage-grace), stop, service restarts,
  rpc.retired.
- SDK plugins in the real core (cli/tests/sdk.rs).

cli/src/host.rs

@@ -17,6 +17,7 @@ pub(crate) struct State {
     pub(crate) processes: HashMap<String, Process>,
     pub(crate) locks: HashMap<String, Lock>,
     pub(crate) native: HashMap<String, NativePlugin>,
+    pub(crate) services: Vec<crate::services::Service>,
 }
 pub(crate) struct Inner {
     pub(crate) world: World,
@@ -26,6 +27,15 @@ pub(crate) struct Inner {
     pub(crate) notifications: tokio::sync::broadcast::Sender<Value>,
     pub(crate) exit: watch::Sender<bool>,
     pub(crate) components: components::Components,
+    /// Calls hold it for reading from the choice of a version until their
+    /// process is in the table. Activation holds it for writing while it
+    /// installs a version, so that it sees every process of the old version.
+    pub(crate) admission: tokio::sync::RwLock<()>,
+    pub(crate) run: sausage_vfs::Memory,
+    pub(crate) graph: Mutex<crate::graph::Graph>,
+    pub(crate) activations: tokio::sync::Mutex<()>,
+    pub(crate) watcher: Mutex<Option<notify::RecommendedWatcher>>,
+    pub(crate) retirements: Mutex<std::collections::HashSet<(String, String)>>,
 }
 #[derive(Clone)]
 /// A cloneable handle to a world and its running processes.
@@ -60,10 +70,17 @@ impl Host {
                 processes: HashMap::new(),
                 locks: HashMap::new(),
                 native: HashMap::new(),
+                services: Vec::new(),
             }),
             notifications: tokio::sync::broadcast::channel(1024).0,
             exit: watch::channel(false).0,
             components: components::Components::default(),
+            admission: tokio::sync::RwLock::new(()),
+            run: sausage_vfs::Memory::default(),
+            graph: Mutex::new(crate::graph::Graph::default()),
+            activations: tokio::sync::Mutex::new(()),
+            watcher: Mutex::new(None),
+            retirements: Mutex::new(std::collections::HashSet::new()),
         }));
         host.boot().await?;
         Ok(host)