This adds a benchmark for deserializing a large transaction that is
often referred to as the megatransaction since it is the largest Bitcoin
transaction mined to date. It consists of 5569 inputs and 1 output and
its hash is:
bb41a757f405890fb0f5856228e23b715702d714d59bf2b1feb70d8b2b4e3e08.
This is being done so there is a benchmark that tests more of a
worst-case scenario which is a better candidate for identifying and
testing improvements.
The following benchmark results shows the how much more intensive this
transaction is over the existing mock transaction:
DeserializeTxSmall 1000000 1751 ns/op 376 B/op 16 allocs/op
DeserializeTxLarge 300 5093980 ns/op 1672829 B/op 33430 allocs/op
