Stop compressing with zlib

While zlib provides good compression results for gossip, it's a dependency
that had a few important CVEs in the past. Some implementations are
reluctant to import it, so we decided to remove it from the specification
in lightning/bolts#981

We stop compressing with zlib and only send uncompressed results, while
still supporting receiving compressed data. We will remove support for
decompression once our monitoring indicates that we stopped receiving
compressed data.

eclair-core/src/main/resources/reference.conf

@@ -230,7 +230,6 @@ eclair {
 
     sync {
       request-node-announcements = true // if true we will ask for node announcements when we receive channel ids that we don't know
-      encoding-type = zlib // encoding for short_channel_ids and timestamps in query channel sync messages; other possible value is "uncompressed"
       channel-range-chunk-size = 1500 // max number of short_channel_ids (+ timestamps + checksums) in reply_channel_range *do not change this unless you know what you are doing*
       channel-query-chunk-size = 100 // max number of short_channel_ids in query_short_channel_ids *do not change this unless you know what you are doing*
     }

eclair-core/src/main/scala/fr/acinq/eclair/NodeParams.scala

@@ -384,11 +384,6 @@ object NodeParams extends Logging {
       case "stop" => UnhandledExceptionStrategy.Stop
     }
 
-    val routerSyncEncodingType = config.getString("router.sync.encoding-type") match {
-      case "uncompressed" => EncodingType.UNCOMPRESSED
-      case "zlib" => EncodingType.COMPRESSED_ZLIB
-    }
-
     val onionMessageRelayPolicy: RelayPolicy = config.getString("onion-messages.relay-policy") match {
       case "no-relay" => NoRelay
       case "channels-only" => RelayChannelsOnly
@@ -493,7 +488,7 @@ object NodeParams extends Logging {
         channelExcludeDuration = FiniteDuration(config.getDuration("router.channel-exclude-duration").getSeconds, TimeUnit.SECONDS),
         routerBroadcastInterval = FiniteDuration(config.getDuration("router.broadcast-interval").getSeconds, TimeUnit.SECONDS),
         requestNodeAnnouncements = config.getBoolean("router.sync.request-node-announcements"),
-        encodingType = routerSyncEncodingType,
+        encodingType = EncodingType.UNCOMPRESSED,
         channelRangeChunkSize = config.getInt("router.sync.channel-range-chunk-size"),
         channelQueryChunkSize = config.getInt("router.sync.channel-query-chunk-size"),
         pathFindingExperimentConf = getPathFindingExperimentConf(config.getConfig("router.path-finding.experiments"))