test: Get rid of default wallet hacks

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

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)

test/functional/feature_dbcrash.py

@@ -56,7 +56,7 @@ class ChainstateWriteCrashTest(BitcoinTestFramework):
         # Set -maxmempool=0 to turn off mempool memory sharing with dbcache
         # Set -rpcservertimeout=900 to reduce socket disconnects in this
         # long-running test
-        self.base_args = ["-limitdescendantsize=0", "-maxmempool=0", "-rpcservertimeout=900", "-dbbatchsize=200000", "-wallet="]
+        self.base_args = ["-limitdescendantsize=0", "-maxmempool=0", "-rpcservertimeout=900", "-dbbatchsize=200000"]
 
         # Set different crash ratios and cache sizes.  Note that not all of
         # -dbcache goes to the in-memory coins cache.
@@ -66,7 +66,7 @@ class ChainstateWriteCrashTest(BitcoinTestFramework):
 
         # Node3 is a normal node with default args, except will mine full blocks
         # and non-standard txs (e.g. txs with "dust" outputs)
-        self.node3_args = ["-blockmaxweight=4000000", "-acceptnonstdtxn", "-wallet="]
+        self.node3_args = ["-blockmaxweight=4000000", "-acceptnonstdtxn"]
         self.extra_args = [self.node0_args, self.node1_args, self.node2_args, self.node3_args]
 
     def skip_test_if_missing_module(self):