Fix CRDT.ORMap gossip/serialization bug

[yim-lee]

Motivation:
See #720

Modifications:
Add defaultValue to ORMap proto so it's included in serialization
and deserialized ORMap would have defaultValue set.

Add test to reproduce error and verify fix.

Result:
No fatal error when gossiping ORMap. Resolves #720

[yim-lee]

An occurrence of #712 and new test:

error: CRDTGossipReplicationClusteredTests.test_gossip_localLWWMapUpdate_toOtherNode : threw error "No result within 10s for block at /code/Tests/DistributedActorsTests/CRDT/CRDTGossipReplicationClusteredTests.swift:287. Queried 1 times, within 10s. Last error: 
        try self.expectMap(probe: p2, expected: ["a": "foo", "aa": .none])
                                                                    �[0;31m^~~~~~~~~~~~~~
error: Did not receive message of type [LWWMap<String, Optional<String>>] within [10s], error: noMessagesInQueue�[0;0m"

5.3 build passes fine though.

@swift-server-bot test this please

[yim-lee]

Don't know why the new test keeps failing in 5.2 but not 5.3.

17:06:51 Captured log [first][2020-07-08 0:6:38.2960] [Gossiper+Shell.swift:257][/system/replicator/gossip] [warning] Failed to ACK delivery [lwwmap] gossip CRDT.Gossip(LWWMap<String, Optional<String>>(["a": Optional("foo"), "aa": nil])) to ActorRef<GossipShell<DistributedActors.CRDT.Gossip, DistributedActors.CRDT.GossipAck>.Message>(sact://second@127.0.0.1:9002/system/replicator/gossip)

[ktoso]

Error logging works but we too aggressively silenced logs in the test's config: 3acc55a#diff-4d7d98ce09adef77b7a83ff0541b8456L23-L25

Going to now view the error on 5.2

[ktoso]

Summary so far: it's about the Swift 5.2 foundation not doing .fragmentsAllowed which causes: Top-level ... encoded as null JSON fragment. whenever a Value is a "not object" (so arrays, ints/doubles, strings). Working around this is somewhat insane with manually parsing the sspecific cases...

The problem only exists on 5.2.4 only on linux (!), and is solved on macos and; on both platforms from swift 5.3...

[yim-lee]

Tracking top-level JSON serialization issue with #729

[yim-lee]

Taking care of ORMap issue with #722