Merge bitcoin/bitcoin#22429: test: refactor: fix segwit terminology (s/witness_program/witness_script/)

8a2b58d test: fix segwit terminology (s/witness_program/witness_script/) (Sebastian Falbesoner)

Pull request description:

  This PR fixes wrong uses of the term "witness program", which according to [BIP141](https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki#Witness_program)  is defined as follows:
  > A scriptPubKey (or redeemScript as defined in BIP16/P2SH) that consists of a 1-byte push opcode (for 0 to 16) followed by a data push between 2 and 40 bytes gets a new special meaning. The value of the first push is called the "version byte". **The following byte vector pushed is called the "witness program".**

  In most cases where "witness program" is used in tests (concerns comments, variable names and in one instance even a function name) what we really want to denote is the "witness script". Thanks to [MarcoFalke for pointing this out in a review comment](bitcoin/bitcoin#22363 (comment))!

  Some historical background: At the time when the P2P segwit tests were first introduced (commit 330b0f3, PR #8149), the term "witness program" was not used consistently in BIP141: https://bitcoin.stackexchange.com/questions/46451/what-is-the-precise-definition-of-witness-program
  This was fixed in PR bitcoin/bips#416 later.

  So in some way, this PR can be seen as a very late follow-up to the BIP141 fix that also reflects these changes in the tests.

ACKs for top commit:
  josibake:
    tACK bitcoin/bitcoin@8a2b58d

Tree-SHA512: f36bb9e53d1b54b86bfa87ec12f33e3ebca64b5f59d97e9662fe35ba12c25e1c9a4f93a5425d0eaa3879dce9e50368d345555b927bfab76945511f873396892b

Author: MarcoFalke