* refactor(test/block): rename large single transaction function
```sh
fastmod single_transaction_block single_transaction_block_many_inputs
```
* rustfmt
* test(block): add a test block with many transparent outputs
* doc(db): explain why we can't just get the UTXOs right before they are deleted
* refactor(db): split out a block data write method
* refactor(block): add a height argument to new_outputs
* test(db): add block and transaction round-trip tests
Including large blocks and transactions.
* test(db): fix large block serialization instability in the tests
* doc(block): add TODOs for generating correct blocks
* Make transparent output functions which take a height test-only
* make sure generated blocks are actually over/under-sized
* replace println!() with an error!() log
This moves the tests::generate module into the block tests. Because
this whole set of changes is just focused on reorganization, the
generate code is unchanged, but in the future, the code should be
rewritten as a collection of proptest strategies.