Gate new splice tlvs on remote support for splicing (#3031)

We do not send splice TLVs to peers that do not advertise splice support to avoid an issue with CLN using the splice TLVs for testing the (experimental) channel upgrade feature.

Author: remyers

eclair-core/src/main/scala/fr/acinq/eclair/channel/fsm/Channel.scala

@@ -2275,9 +2275,10 @@ class Channel(val nodeParams: NodeParams, val wallet: OnChainChannelFunder with
         }
         case _ => Set.empty
       }
-      val lastFundingLockedTlvs: Set[ChannelReestablishTlv] =
+      val lastFundingLockedTlvs: Set[ChannelReestablishTlv] = if (d.commitments.params.remoteParams.initFeatures.hasFeature(Features.SplicePrototype)) {
           d.commitments.lastLocalLocked_opt.map(c => ChannelReestablishTlv.MyCurrentFundingLockedTlv(c.fundingTxId)).toSet ++
             d.commitments.lastRemoteLocked_opt.map(c => ChannelReestablishTlv.YourLastFundingLockedTlv(c.fundingTxId)).toSet
+      } else Set.empty
 
       val channelReestablish = ChannelReestablish(
         channelId = d.channelId,

eclair-core/src/test/scala/fr/acinq/eclair/channel/states/e/OfflineStateSpec.scala

@@ -945,6 +945,7 @@ class OfflineStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLike with
 
     // Alice will resend her channel_ready on reconnection because the channel hasn't been used for any payment yet (pre-splice behavior).
     alice2bob.expectMsgType[ChannelReady]
+    bob2alice.expectMsgType[ChannelReady]
     alice2bob.expectNoMessage(100 millis)
 
     // we update the channel
@@ -1015,6 +1016,8 @@ class OfflineStateSpec extends TestKitBaseClass with FixtureAnyFunSuiteLike with
     bob2alice.expectMsgType[ChannelReestablish]
     bob2alice.forward(alice)
     alice2bob.forward(bob)
+    bob2alice.expectMsgType[ChannelReady]
+    bob2alice.forward(alice)
 
     // Alice will NOT resend their channel_ready at reconnection because she has received bob's announcement_signatures (pre-splice behavior).
     alice2bob.expectNoMessage(100 millis)