BrokerStore<->Zeek table - introdude &backend attribute

The &backend attribute allows for a much more convenient way of
interacting with brokerstores. One does not need to create a broker
store anymore - instead all of this is done internally.

The current state of this partially works. This should work fine for
persistence - but clones are currently not yet correctly attached.

scripts/base/frameworks/broker/store.zeek

@@ -25,6 +25,10 @@ export {
 	## A negative/zero value indicates to never buffer commands.
 	const default_clone_mutation_buffer_interval = 2min &redef;
 
+	const auto_store_master = T &redef;
+
+	const auto_store_db_directory = "." &redef;
+
 	## Whether a data store query could be completed or not.
 	type QueryStatus: enum {
 		SUCCESS,

scripts/base/frameworks/cluster/main.zeek

@@ -249,6 +249,10 @@ export {
 	global nodeid_topic: function(id: string): string;
 }
 
+@if ( Cluster::is_enabled() && Cluster::local_node_type() != Cluster::MANAGER ) )
+redef Broker::store_master = T;
+@endif
+
 global active_worker_ids: set[string] = set();
 
 type NamedNode: record {