Round-trip and benchmark large transparent, sprout, sapling, and orchard blocks

[teor2345]

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

Zebra's existing unit tests do round-trip parsing tests for:

• a large block with a single large transparent transaction with many inputs
• a large block with many small transparent transactions

In #2018, we add benchmarks for these large blocks.

In #1979, we add the equivalent orchard tests.

That just leaves Sapling, Sprout, and many large outputs.

Describe the solution you'd like

Write a round-trip unit test and serialization benchmarks for:

• Transparent
  • a large block with a single large transparent transaction with many outputs
  • a large block with many small transparent transactions
• Sapling
  • a large block with a single large transparent transaction with many inputs
  • a large block with a single large transparent transaction with many outputs
  • a large block with many small transparent transactions
• Sprout
  • a large block with a single large transparent transaction with many joinsplits
  • a large block with many small transparent transactions

Describe alternatives you've considered

This is a low-priority change that increases test and benchmark coverage.

[teor2345]

This is a useful idea, but we don't need it any time soon.