coin selection: heap-ify SRD, don't return selection if exceeds max tx weight

Uses a min-effective-value heap, so we can remove the least valuable input/s
while the selected weight exceeds the maximum allowed weight.

Co-authored-by: Murch <murch@murch.one>

src/wallet/test/fuzz/coinselection.cpp

@@ -90,7 +90,7 @@ FUZZ_TARGET(coinselection)
     // Run coinselection algorithms
     const auto result_bnb = SelectCoinsBnB(group_pos, target, cost_of_change);
 
-    auto result_srd = SelectCoinsSRD(group_pos, target, fast_random_context);
+    auto result_srd = SelectCoinsSRD(group_pos, target, fast_random_context, MAX_STANDARD_TX_WEIGHT);
     if (result_srd) result_srd->ComputeAndSetWaste(cost_of_change, cost_of_change, 0);
 
     CAmount change_target{GenerateChangeTarget(target, coin_params.m_change_fee, fast_random_context)};