Serve a module's log verbs so its record outlives a bucket's cap and the events' week (ADR 0297, issues 501, 502)

The runtime answers mesh/log.append, read, last and info for a log issued
in the module's membership, by publish, batch direct get and stream info
alone. A stale expect is refused as a lost state update, so a module tells
it by the same code.

node-tools/internal/launch/event_answer_test.go

@@ -37,6 +37,7 @@ type subscribing struct {
 func (b *subscribing) Publish(json.RawMessage) error                          { return nil }
 func (b *subscribing) Ask(json.RawMessage) (json.RawMessage, error)           { return nil, nil }
 func (b *subscribing) State(string, json.RawMessage) (json.RawMessage, error) { return nil, nil }
+func (b *subscribing) Log(string, json.RawMessage) (json.RawMessage, error)   { return nil, nil }
 func (b *subscribing) Watch(json.RawMessage, func(json.RawMessage) error) (func(), error) {
 	return func() {}, nil
 }