test: refactor: use create_block parameters

Summary:
Passing a list of transactions txlist to create_block appends
them to the block, hence we don't need to do that manually anymore.
The merkle root calculation can also be removed, since this is done
in the end of the helper.

This is a backport of core#23521
Notes:

• We need to specify version=4 explicitly (missing backport: core#16333)
• The txlist parameter to create_block is from core#19401, it was skipped in D10688 (because unused at the time).
• We also move the tx ctor sorting code to create_block

Test Plan: ninja check-functional-extended

Reviewers: #bitcoin_abc, roqqit

Reviewed By: #bitcoin_abc, roqqit

Differential Revision: https://reviews.bitcoinabc.org/D17691