Send multiple notes at once

Should the note transport layer allow for multiple notes to be sent at once?
From the client, it would be nice to be able to batch-send all the output notes of a single transaction.

Look at the note transport layer code to understand the current single-note sending mechanism. Examine client transaction output handling to see how notes are currently collected and sent. Determine the API changes needed for batch sending, including any serialization/deserialization updates. Check for existing tests related to note transmission to understand the validation requirements.

Written by the indexing model from the issue text.