chainparams: add blockhash to AssumeutxoData

This allows us to reference assumeutxo configuration by blockhash as
well as height; this is helpful in future changes when we want to
reference assumeutxo configurations before the block index is loaded.

src/util/vector.h

@@ -5,7 +5,9 @@
 #ifndef BITCOIN_UTIL_VECTOR_H
 #define BITCOIN_UTIL_VECTOR_H
 
+#include <functional>
 #include <initializer_list>
+#include <optional>
 #include <type_traits>
 #include <utility>
 #include <vector>
@@ -67,4 +69,15 @@ inline void ClearShrink(V& v) noexcept
     V{}.swap(v);
 }
 
+template<typename V, typename L>
+inline std::optional<V> FindFirst(const std::vector<V>& vec, const L fnc)
+{
+    for (const auto& el : vec) {
+        if (fnc(el)) {
+            return el;
+        }
+    }
+    return std::nullopt;
+}
+
 #endif // BITCOIN_UTIL_VECTOR_H