Merge #20034: test: Get rid of default wallet hacks

c1585bca8d test: Get rid of default wallet hacks (Russell Yanofsky)
ed3acda33b test, refactor: add default_wallet_name and wallet_data_filename variables (Russell Yanofsky)

Pull request description:

  Changes:

  - Get rid of setup_nodes (`-wallet`, `-nowallet`, `-disablewallet`) argument rewriting
  - Get rid of hardcoded wallet `""` names and `-wallet=""` args

  Motivation:

  - Simplify test framework behavior so it's easier to write new tests without having arguments mangled by the framework
  - Make tests more readable, replacing unexplained `""` string literals with `default_wallet_name` references
  - Make it trivial to update default wallet name and wallet data filename for sqlite #19077 testing
  - Stop relying on `-wallet` arguments to create wallets, so it is easy to change `-wallet` option in the future to only load existing wallets not create new ones (to avoid accidental wallet creation, and encourage use of wallet encryption and descriptor features)

ACKs for top commit:
  MarcoFalke:
    ACK c1585bca8d, only effective change is adding documentation 🎵

Tree-SHA512: f62dec7cbdacb5f330aa0e1eec89ab4d065540d91495bbedcb375eda1c080b45ce9edb310ce253c44c4839f1b4cc2c7df9816c58402d5d43f94a437e301ea8bc

test/functional/feature_config_args.py

@@ -14,6 +14,7 @@ class ConfArgsTest(BitcoinTestFramework):
         self.setup_clean_chain = True
         self.num_nodes = 1
         self.supports_cli = False
+        self.wallet_names = []
 
     def test_config_file_parser(self):
         # Assume node is stopped