Merge bitcoin#30134: fuzz: add more coverage for ScriptPubKeyMan

e3249f2 fuzz: add more coverage for `ScriptPubKeyMan` (brunoerg)

Pull request description:

  This PR adds more coverage for `ScriptPubKeyMan`:

  - Check `GetKey` and `HasPrivKey` after adding descriptor key.
  - Cover `GetEndRange` and `GetKeyPoolSize`.
  - Cover `MarkUnusedAddresses` with the scripts from ScriptPubKeys and `GetMetadata` with the destinations from them.

ACKs for top commit:
  marcofleon:
    Tested ACK e3249f2. I ran the updated harness for ~9 hours on an empty corpus, generated a coverage report, and checked that the new functions mentioned were hit. Coverage of `scriptpubkeyman.cpp` increased.
  murchandamus:
    Tested ACK e3249f2

Tree-SHA512: cfab91f6c8401174842e79209c0e9225c08f011fe9b41d0a58bcec716ae4545eaf803867f899ed7b5fbcefea45711f91894e36df082ba19732dd310cd9e61a79

src/wallet/test/fuzz/scriptpubkeyman.cpp

@@ -137,6 +137,15 @@ FUZZ_TARGET(scriptpubkeyman, .init = initialize_spkm)
                                            PKHash{ConsumeUInt160(fuzzed_data_provider)}};
                         std::string str_sig;
                         (void)spk_manager->SignMessage(msg, pk_hash, str_sig);
+                        (void)spk_manager->GetMetadata(dest);
+                    }
+                }
+            },
+            [&] {
+                auto spks{spk_manager->GetScriptPubKeys()};
+                for (const CScript& spk : spks) {
+                    if (fuzzed_data_provider.ConsumeBool()) {
+                        spk_manager->MarkUnusedAddresses(spk);
                     }
                 }
             },
@@ -148,6 +157,10 @@ FUZZ_TARGET(scriptpubkeyman, .init = initialize_spkm)
                 }
                 spk_manager->AddDescriptorKey(key, key.GetPubKey());
                 spk_manager->TopUp();
+                LOCK(spk_manager->cs_desc_man);
+                auto particular_key{spk_manager->GetKey(key.GetPubKey().GetID())};
+                assert(*particular_key == key);
+                assert(spk_manager->HasPrivKey(key.GetPubKey().GetID()));
             },
             [&] {
                 std::string descriptor;
@@ -194,6 +207,9 @@ FUZZ_TARGET(scriptpubkeyman, .init = initialize_spkm)
             }
         );
     }
+
+    (void)spk_manager->GetEndRange();
+    (void)spk_manager->GetKeyPoolSize();
 }
 
 } // namespace