IFrame widget improvements (#15483)

changes - 
- make iframe side panel to match others -- ie use SidePanelHeader for
title
- make url optional in configuration to match that of the other widgets
(allow partial saves) - render No data status when error or no url
- split widget sizes into two -- graph widget sizes and widget sizes
(graph widgets are a subset of chart widgets)

packages/twenty-front/src/generated-metadata/graphql.ts

@@ -1519,7 +1519,7 @@ export enum IdentityProviderType {
 
 export type IframeConfiguration = {
   __typename?: 'IframeConfiguration';
-  url: Scalars['String'];
+  url?: Maybe<Scalars['String']>;
 };
 
 export type ImapSmtpCaldavConnectionParameters = {