[Pset] More integration tests

[altafan]

We should create more tests for pset in order to increase the number of use cases covered by this package. Just to give an idea, we miss a test that creates a CT transaction with CT inputs and CT outputs.

A more detailed list will be defined soon.

[altafan]

List of possible transaction:

• unblinded tx
• unblinded issuance tx
• blinded tx - only outputs
• blinded tx - inputs and outputs
• blinded issuance tx - only outputs
• blinded issuance tx - inputs and outputs

Also, existing tests use only P2WPKH inputs and we should test also the other types of inputs:

• p2pkh
• p2sh(p2wpkh)
• p2sh(p2ms)
• p2wsh(p2ms)

Given that, if we do some calculations, we have a total of 30 test cases, while we actually implemented 5 yet. We should also consider to refactor pset_test.go in order to reuse as much of code as possible or it will become a real jungle for someone to read this file.

[altafan]

closed by #134.