[Task]: Refactor note-related messages to include a NoteMetadata

[igamigo]

Node's components affected by this task

• RPC
• Block producer
• Store
• Protobuf messages
• Testing

What should be done?

Currently note-related messages in protobuf contain the same fields. These should be refactored out into its own NoteMetadata object

How should it be done?

https://github.com/0xPolygonMiden/miden-node/blob/25529ac9bc629e4ac1f0d2c8bc9739b0d1bc2866/proto/proto/note.proto

Change messages to include a new NoteMetadata field that looks something like this:

message NoteMetadata {
    account.AccountId sender  = 1;
    uint32 note_type = 2;
    fixed32 tag = 3;
    fixed64 aux = 4; // unsure if we want/need this for a first iteration
}

and replaces the pertinent fields.

When is this task done?

When note messages contain NoteMetadata as a specific field.

Additional context

No response

[bobbinth]

Closed by #338.