Create Sapling-only transaction v5 test vectors

[teor2345]

Is your feature request related to a problem? Please describe.

There are no hard-coded serialized Transaction v5 test vectors yet.

Describe the solution you'd like

Create or obtain at least one of each of the following types of test vectors:

• Sapling only
• Transparent only
• Sapling/Transparent
  • shielding (transparent to sapling)
  • unshielding (sapling to transparent)
• an empty v5 transaction (which will fail the "at least one transfer" consensus rule)

All these test vectors should have empty orchard actions sections.

• Make sure zcashd and Zebra are using the same test vectors
• Add the test vectors to ZIP-225: https://zips.z.cash/zip-0225

Describe alternatives you've considered

Do nothing - we might discover incompatibilities when we deploy on testnet or mainnet.

We could wait for zcashd to create test vectors, and use theirs.

[teor2345]

@oxarbitrage if you're blocked on the Orchard parsing you could do the sapling test vectors instead.

[teor2345]

We've effectively covered these cases using a fake v5 transaction conversion function, and the empty v5 transaction creation function.