refactor(workspace): split workspace interface and implementation (#5463)

@affine/workspace -> (@affine/workspace, @affine/workspace-impl)

packages/common/workspace/src/factory.ts

@@ -0,0 +1,13 @@
+import type { WorkspaceMetadata } from './metadata';
+import type { Workspace } from './workspace';
+
+export interface WorkspaceFactory {
+  name: string;
+
+  openWorkspace(metadata: WorkspaceMetadata): Workspace;
+
+  /**
+   * get blob without open workspace
+   */
+  getWorkspaceBlob(id: string, blobKey: string): Promise<Blob | null>;
+}