index: Enable reindex-chainstate with active indexes

This is achieved by letting the index sync thread wait until
reindex-chainstate is finished.

This also disables the pruning check when reindexing the chainstate (which is
incompatible with prune mode) because there would be no chain at this point
in init.

src/test/util/setup_common.cpp

@@ -155,6 +155,7 @@ BasicTestingSetup::BasicTestingSetup(const ChainType chainType, const std::vecto
         noui_connect();
         noui_connected = true;
     }
+    node::g_indexes_ready_to_sync = true;
 }
 
 BasicTestingSetup::~BasicTestingSetup()