lightningd: enable peer storage by default,

Now we've make it only on existing channels, and not have to call
listdatastore every time, that means we can safely turn it on by
default.

Changelog-Added: Protocol: we now offer peer storage to any peers who create a channel.
Changelog-Deprecated: Config: `--experimental-peer-storage` (it's now the default).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

lightningd/lightningd.c

@@ -931,6 +931,7 @@ static struct feature_set *default_features(const tal_t *ctx)
 		OPTIONAL_FEATURE(OPT_ONION_MESSAGES),
 		OPTIONAL_FEATURE(OPT_CHANNEL_TYPE),
 		OPTIONAL_FEATURE(OPT_ROUTE_BLINDING),
+		OPTIONAL_FEATURE(OPT_PROVIDE_STORAGE),
 		/* Removed later for elements */
 		OPTIONAL_FEATURE(OPT_ANCHORS_ZERO_FEE_HTLC_TX),
 	};