Add instance experimental setting for isolated workspaces

Introduce a singleton instance_settings store and experimental settings API, add the Experimental instance settings page, and gate execution workspace behavior behind the new enableIsolatedWorkspaces flag.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/db/src/migrations/meta/_journal.json

@@ -253,6 +253,13 @@
       "when": 1773698696169,
       "tag": "0035_marvelous_satana",
       "breakpoints": true
+    },
+    {
+      "idx": 36,
+      "version": "7",
+      "when": 1773756213455,
+      "tag": "0036_cheerful_nitro",
+      "breakpoints": true
     }
   ]
-}
+}