[ZIP 317] nZSAIssueNotes, nAssetCreations, nMemoChunks are not well-defined

[daira]

Reference [3] is to § 7.1 Transaction Encoding and Consensus in version 2022.3.8 of the protocol spec, which does not define these fields.

Also,

• nJoinSplit should be defined as 0 for transactions before v2 or after v4.
• nSpendsSapling and nOutputsSapling should be defined as 0 for transactions before v4.
• nActionsOrchard should be defined as 0 for transactions before v5.