fuzz: move the coins_view target's body into a standalone function

We'll reuse it for a target where the coins view is a DB.

Author: darosior

src/test/fuzz/coins_view.cpp

@@ -14,6 +14,7 @@
 #include <test/fuzz/fuzz.h>
 #include <test/fuzz/util.h>
 #include <test/util/setup_common.h>
+#include <txdb.h>
 #include <util/hasher.h>
 
 #include <cassert>
@@ -41,12 +42,10 @@ void initialize_coins_view()
     static const auto testing_setup = MakeNoLogFileContext<>();
 }
 
-FUZZ_TARGET(coins_view, .init = initialize_coins_view)
+void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsView& backend_coins_view)
 {
-    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
     bool good_data{true};
 
-    CCoinsView backend_coins_view;
     CCoinsViewCache coins_view_cache{&backend_coins_view, /*deterministic=*/true};
     COutPoint random_out_point;
     Coin random_coin;
@@ -294,3 +293,10 @@ FUZZ_TARGET(coins_view, .init = initialize_coins_view)
             });
     }
 }
+
+FUZZ_TARGET(coins_view, .init = initialize_coins_view)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    CCoinsView backend_coins_view;
+    TestCoinsView(fuzzed_data_provider, backend_coins_view);
+}