bitcoin/chainparams: add an utility to retrieve chainparams for all networks

bitcoin/chainparams.h

@@ -46,6 +46,12 @@ struct chainparams {
  */
 const struct chainparams *chainparams_for_network(const char *network_name);
 
+/**
+ * chainparams_for_networks - Get blockchain parameters for all known networks,
+ *                            as a tal array.
+ */
+const struct chainparams **chainparams_for_networks(const tal_t *ctx);
+
 /**
  * chainparams_by_bip173 - Helper to get a network by its bip173 name
  *