Update the maximum size of the consent storage

The current limitation of 1200 chars is already too small for most publishers.

Here is the projection we used to update this storage:
- 1000 publishers in the global vendor list, using publisher restrictions: the size of the consent string should be of 3233 chars.
- The current additionnal consents strings, stored in the metadata field of the consent object, is 3079 chars long

This leaves an empty space of 688 chars, to the other data stored in the object.

Fixes ampproject#31673

extensions/amp-consent/0.1/consent-state-manager.js

@@ -38,7 +38,7 @@ import {expandConsentEndpointUrl, getConsentCID} from './consent-config';
 const TAG = 'CONSENT-STATE-MANAGER';
 
 /** @visibleForTesting */
-export const CONSENT_STORAGE_MAX = 1200;
+export const CONSENT_STORAGE_MAX = 7000;
 
 export class ConsentStateManager {
   /**