Use std::vector API for construction of test data.
Use std::vector API for construction of test data.

Summary:
> For constructing test scripts, use std::vector and, in particular,
> std::vector::insert to insert 20 zero bytes rather than listing the full
> array of bytes explicitly.  This makes the code easier to read and makes
> it immediately obvious what the structure of the data is, without having
> to count the zeros to understand it.

This is a backport of Core [[https://github.com/bitcoin/bitcoin/pull/15099 | PR15099]] and [[https://github.com/bitcoin/bitcoin/pull/17254 | PR17254]]

[[https://github.com/bitcoin/bitcoin/pull/17254 | PR17254]] adds back opcodes lost in the fist PR.

Test Plan: `ninja && ninja check`

Reviewers: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D8236

Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc,Bitcoin-ABC/bitcoin-abc