Using mutable default arguments (lists, dicts) in python is usually a very bad idea.
https://florimond.dev/blog/articles/2018/08/python-mutable-defaults-are-the-source-of-all-evil/

This fixes a few instances in the main CI test directory, and adds a linter to detect new cases.
I found some more cases in contrib/buildbot and contrib/teamcity, that I would like to address in a separate diff because they are a bit trickier to investigate and harder to debug.

Backport of Core PR16726

ninja && ninja check-functional

arc lint --everything, to make sure there are no false positive.

Example of detection (mutable default parameter added on purpose):

>>> Lint for test/functional/abc-transaction-ordering.py:


   Warning  (PYTHON_MUTABLE_DEFAULT1) Mutable default arguments should generally not be used in python.
    Found mutable default argument in function.

              49         self.blocks = {}
              50         self.extra_args = [['-whitelist=127.0.0.1']]
              51 
    >>>       52     def add_transactions_to_block(self, block, tx_list=[]):
              53         [tx.rehash() for tx in tx_list]
              54         block.vtx.extend(tx_list)
              55

I also tested it with dictionaries or set literals, and functions with parameters on multiple lines.