wallet: avoid locking cs_wallet throughout Create's entire scope

Implement portions of f13a22a (bitcoin#22868) to sidestep inconsistent
lock order by further scoping `cs_wallet` and exiting that scope before
locking `cs_wallet_manager_map`

```
POTENTIAL DEADLOCK DETECTED
  Previous lock order was:
    (2) 'walletInstance->cs_wallet' in wallet/wallet.cpp:4932 (in thread 'init')
    (1) 'm_walletman.cs_wallet_manager_map' in coinjoin/interfaces.cpp:72 (in thread 'init')
  Current lock order is:
    (1) 'm_walletman.cs_wallet_manager_map' in coinjoin/interfaces.cpp:72 (in thread 'init')
    (2) 'cs_wallet' in wallet/wallet.cpp:5530 (in thread 'init')

```

Additionally, don't bother to see if the wallet is locked when doing a
re-init of CoinJoin, just stop mixing (it'll restart anyway if
`-coinjoinautostart` is set) because we're working from wallet code and
it's very likely that calls to the CoinJoin interface will already hold
a `cs_wallet`.

Which is a problem because re-init'ing involves going through every
wallet and stopping the mix process. If we check to see if the wallet is
locked first, it involves locking `cs_wallet` briefly.

If we're already holding `cs_wallet`, the order is `cs_wallet` and then
`cs_wallet_manager_map` but if we *don't* hold any `cs_wallet`, then the
order will reverse because we still need to lock `cs_wallet` to see if
it's locked, which spells trouble for us.

src/wallet/init.cpp

@@ -211,10 +211,8 @@ void WalletInit::InitCoinJoinSettings(const CoinJoinWalletManager& cjwalletman)
     bool fAutoStart = gArgs.GetBoolArg("-coinjoinautostart", DEFAULT_COINJOIN_AUTOSTART);
     for (auto& pwallet : GetWallets()) {
         auto manager = cjwalletman.Get(pwallet->GetName());
-        assert(manager != nullptr);
-        if (pwallet->IsLocked()) {
-            manager->StopMixing();
-        } else if (fAutoStart) {
+        Assert(manager)->StopMixing();
+        if (fAutoStart) {
             manager->StartMixing();
         }
     }

src/wallet/test/wallet_tests.cpp

@@ -1298,18 +1298,14 @@ BOOST_FIXTURE_TEST_CASE(CreateWallet, TestChain100Setup)
     // deadlock during the sync and simulates a new block notification happening
     // as soon as possible.
     addtx_count = 0;
-    auto handler = HandleLoadWallet([&](std::unique_ptr<interfaces::Wallet> wallet) EXCLUSIVE_LOCKS_REQUIRED(wallet->wallet()->cs_wallet, cs_wallets) {
+    auto handler = HandleLoadWallet([&](std::unique_ptr<interfaces::Wallet> wallet) {
             BOOST_CHECK(rescan_completed);
             m_coinbase_txns.push_back(CreateAndProcessBlock({}, GetScriptForRawPubKey(coinbaseKey.GetPubKey())).vtx[0]);
             block_tx = TestSimpleSpend(*m_coinbase_txns[2], 0, coinbaseKey, GetScriptForRawPubKey(key.GetPubKey()));
             m_coinbase_txns.push_back(CreateAndProcessBlock({block_tx}, GetScriptForRawPubKey(coinbaseKey.GetPubKey())).vtx[0]);
             mempool_tx = TestSimpleSpend(*m_coinbase_txns[3], 0, coinbaseKey, GetScriptForRawPubKey(key.GetPubKey()));
             BOOST_CHECK(m_node.chain->broadcastTransaction(MakeTransactionRef(mempool_tx), DEFAULT_TRANSACTION_MAXFEE, false, error));
-            LEAVE_CRITICAL_SECTION(cs_wallets);
-            LEAVE_CRITICAL_SECTION(wallet->wallet()->cs_wallet);
             SyncWithValidationInterfaceQueue();
-            ENTER_CRITICAL_SECTION(wallet->wallet()->cs_wallet);
-            ENTER_CRITICAL_SECTION(cs_wallets);
         });
     wallet = TestLoadWallet(m_node);
     BOOST_CHECK_EQUAL(addtx_count, 4);

src/wallet/wallet.cpp

@@ -4929,6 +4929,7 @@ std::shared_ptr<CWallet> CWallet::Create(interfaces::Chain& chain, interfaces::C
     // Try to top up keypool. No-op if the wallet is locked.
     walletInstance->TopUpKeyPool();
 
+    {
     LOCK(walletInstance->cs_wallet);
 
     // Register wallet with validationinterface. It's done before rescan to avoid
@@ -5009,6 +5010,7 @@ std::shared_ptr<CWallet> CWallet::Create(interfaces::Chain& chain, interfaces::C
         walletInstance->chainStateFlushed(chain.getTipLocator());
         walletInstance->GetDatabase().IncrementUpdateCounter();
     }
+    } // LOCK(walletInstance->cs_wallet)
 
     coinjoin_loader.AddWallet(*walletInstance);
 
@@ -5019,9 +5021,9 @@ std::shared_ptr<CWallet> CWallet::Create(interfaces::Chain& chain, interfaces::C
         }
     }
 
-    walletInstance->SetBroadcastTransactions(gArgs.GetBoolArg("-walletbroadcast", DEFAULT_WALLETBROADCAST));
-
     {
+        LOCK(walletInstance->cs_wallet);
+        walletInstance->SetBroadcastTransactions(gArgs.GetBoolArg("-walletbroadcast", DEFAULT_WALLETBROADCAST));
         walletInstance->WalletLogPrintf("setExternalKeyPool.size() = %u\n",   walletInstance->KeypoolCountExternalKeys());
         walletInstance->WalletLogPrintf("GetKeyPoolSize() = %u\n",   walletInstance->GetKeyPoolSize());
         walletInstance->WalletLogPrintf("mapWallet.size() = %u\n",            walletInstance->mapWallet.size());