Merge bitcoin#17319: Tests: remove bignum module

3ed772d [tests] remove bignum.py (John Newbery)
f950ec2 [tests] remove bn2bin() (John Newbery)
3b9b385 [tests] remove bn_bytes() function (John Newbery)
a760aa1 [tests] remove mpi2vch() function (John Newbery)
9a60bef [tests] don't encode the integer size in bignum (John Newbery)
1dc68ae [tests] add function comments to bignum (John Newbery)
f31fc0e [tests] fix flake8 warnings in script.py and bignum.py (John Newbery)

Pull request description:

  Only one function is imported in script.py. Just move that function to script.py and remove the bignum.py module.

  Remove unused functionality and fix some flake8 warnings along the way.

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Tree-SHA512: 015f543ab545b5d5451896e2751d9c19334d9155b03faacd2023781e89833a2440f7f28741e9a8ac49badd9cdc012cbb6e038cdcdebeefaf9cb9d461c0689157

Author: MarcoFalke

test/functional/README.md

@@ -134,9 +134,6 @@ Utilities for manipulating transaction scripts (originally from python-bitcoinli
 #### [key.py](test_framework/key.py)
 Test-only secp256k1 elliptic curve implementation
 
-#### [bignum.py](test_framework/bignum.py)
-Helpers for script.py
-
 #### [blocktools.py](test_framework/blocktools.py)
 Helper functions for creating blocks and transactions.