rpc: deprecate addresses and reqSigs from rpc outputs

1) add a new sane "address" field (for outputs that have an
   identifiable address, which doesn't include bare multisig)
2) with -deprecatedrpc: leave "reqSigs" and "addresses" intact
   (with all weird/wrong behavior they have now)
3) without -deprecatedrpc: drop "reqSigs" and "addresses" entirely,
   always.

test/functional/rpc_createmultisig.py

@@ -165,7 +165,7 @@ class RpcCreateMultiSigTest(BitcoinTestFramework):
         txid = node0.sendtoaddress(madd, 40)
 
         tx = node0.getrawtransaction(txid, True)
-        vout = [v["n"] for v in tx["vout"] if madd in v["scriptPubKey"].get("addresses", [])]
+        vout = [v["n"] for v in tx["vout"] if madd == v["scriptPubKey"]["address"]]
         assert len(vout) == 1
         vout = vout[0]
         scriptPubKey = tx["vout"][vout]["scriptPubKey"]["hex"]