feat(infra): new workspace infra (#5617)

This PR copying @affine/workspace into common/infra, and adding definitions for services and unit tests.

packages/common/infra/src/utils/merge-updates.ts

@@ -0,0 +1,17 @@
+import { applyUpdate, Doc, encodeStateAsUpdate } from 'yjs';
+
+export function mergeUpdates(updates: Uint8Array[]) {
+  if (updates.length === 0) {
+    return new Uint8Array();
+  }
+  if (updates.length === 1) {
+    return updates[0];
+  }
+  const doc = new Doc();
+  doc.transact(() => {
+    updates.forEach(update => {
+      applyUpdate(doc, update);
+    });
+  });
+  return encodeStateAsUpdate(doc);
+}