test: bugfix, coinselector_test, use 'CoinsResult::Erase/Add' instead of direct member access

Aside from the cleanup, this solves a bug in the following-up commit. Because, in these
tests, we are manually adding/erasing outputs from the CoinsResult object but never
updating the internal total amount field.

Author: furszy

src/wallet/test/coinselector_tests.cpp

@@ -83,7 +83,7 @@ static void add_coin(CoinsResult& available_coins, CWallet& wallet, const CAmoun
     assert(ret.second);
     CWalletTx& wtx = (*ret.first).second;
     const auto& txout = wtx.tx->vout.at(nInput);
-    available_coins.coins[OutputType::BECH32].emplace_back(COutPoint(wtx.GetHash(), nInput), txout, nAge, CalculateMaximumSignedInputSize(txout, &wallet, /*coin_control=*/nullptr), /*spendable=*/ true, /*solvable=*/ true, /*safe=*/ true, wtx.GetTxTime(), fIsFromMe, feerate);
+    available_coins.Add(OutputType::BECH32, {COutPoint(wtx.GetHash(), nInput), txout, nAge, CalculateMaximumSignedInputSize(txout, &wallet, /*coin_control=*/nullptr), /*spendable=*/ true, /*solvable=*/ true, /*safe=*/ true, wtx.GetTxTime(), fIsFromMe, feerate});
 }
 
 /** Check if SelectionResult a is equivalent to SelectionResult b.
@@ -342,7 +342,7 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         coin_control.Select(select_coin.outpoint);
         PreSelectedInputs selected_input;
         selected_input.Insert(select_coin, coin_selection_params_bnb.m_subtract_fee_outputs);
-        available_coins.coins[OutputType::BECH32].erase(available_coins.coins[OutputType::BECH32].begin());
+        available_coins.Erase({available_coins.coins[OutputType::BECH32].begin()->outpoint});
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(0);
         const auto result10 = SelectCoins(*wallet, available_coins, selected_input, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(result10);
@@ -402,7 +402,7 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         coin_control.Select(select_coin.outpoint);
         PreSelectedInputs selected_input;
         selected_input.Insert(select_coin, coin_selection_params_bnb.m_subtract_fee_outputs);
-        available_coins.coins[OutputType::BECH32].erase(++available_coins.coins[OutputType::BECH32].begin());
+        available_coins.Erase({(++available_coins.coins[OutputType::BECH32].begin())->outpoint});
         const auto result13 = SelectCoins(*wallet, available_coins, selected_input, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(EquivalentResult(expected_result, *result13));
     }
@@ -974,7 +974,7 @@ BOOST_AUTO_TEST_CASE(SelectCoins_effective_value_test)
     cc.SelectExternal(output.outpoint, output.txout);
 
     const auto preset_inputs = *Assert(FetchSelectedInputs(*wallet, cc, cs_params));
-    available_coins.coins[OutputType::BECH32].erase(available_coins.coins[OutputType::BECH32].begin());
+    available_coins.Erase({available_coins.coins[OutputType::BECH32].begin()->outpoint});
 
     const auto result = SelectCoins(*wallet, available_coins, preset_inputs, target, cc, cs_params);
     BOOST_CHECK(!result);