Disallow creating or updating a record without any data.

[LiranCohen]

Prior to TBD54566975/dwn-sdk-js#629, dwn-sdk-js would return an error if you attempted to write a record without any data.

But now that we allow initial writes to be written without data, but not returned in a query, this could cause some confusion/errors as @csuwildcat has experienced.

• records.write(...) in DwnApi should throw if no data is provided.
• record.update(...) in Record should throw if no data is provided.