Change readonly instance props of DurableObjectState to lazy-writable.

This is really two changes:

1. Make these lazy properties. This is a strict win since the properties cannot change value during the lifetime of the object, so there's no reason to call into C++ on every access. This might even be a non-negligible performance gain for people who use `ctx.storage` a lot without memoizing it.

2. Make them writable. There's no real reason to prevent people from overwriting these if they really want to. Moreover, introducing `container` as a read-only property could arguably break someone who is, for whatever reason, monkey-patching this property in today.

src/workerd/api/actor-state.h

@@ -541,9 +541,9 @@ class DurableObjectState: public jsg::Object {
 
   JSG_RESOURCE_TYPE(DurableObjectState, CompatibilityFlags::Reader flags) {
     JSG_METHOD(waitUntil);
-    JSG_READONLY_INSTANCE_PROPERTY(id, getId);
-    JSG_READONLY_INSTANCE_PROPERTY(storage, getStorage);
-    JSG_READONLY_INSTANCE_PROPERTY(container, getContainer);
+    JSG_LAZY_INSTANCE_PROPERTY(id, getId);
+    JSG_LAZY_INSTANCE_PROPERTY(storage, getStorage);
+    JSG_LAZY_INSTANCE_PROPERTY(container, getContainer);
     JSG_METHOD(blockConcurrencyWhile);
     JSG_METHOD(acceptWebSocket);
     JSG_METHOD(getWebSockets);