Update `messages` and `stateful-storage` pallets to support Intents

[JoeCap08055]

Description

Both the messages and stateful-storage pallets will need to transition to using IntentId as the primary index for on-chain storage, instead of SchemaId. While the values will not change, as the schemas pallet migration ensures that there will initially be a 1:1 mapping between existing schemas and intents with the same numeric IDs, going forward there will be a 1:many mapping of IntentId:SchemaId, so that schema_id needs to be added to the stored payload.

A/C

• [ ] Existing message storage can be read & the schema_id determined
• [ ] Any new messages stored have schema_id stored as part of the payload
• [ ] Existing stateful-storage payloads can be read & the schema_id determined
• [ ] Any new stateful-storage payloads written, whether Paginated or Itemized, include schema_id as part of the item or page write, so that it can be read back.