One bus: the AMQP transport is gone from the controller

The mesh runs on the seat's bus alone (novox/hq ADR 0131, design 28 task 5.5). The old
transport's consume loop, build request, tool ask, management API and account scoping are
deleted, and the bus switch with them; the controller connects to the broker seat and to
nothing else. The store-window tests keep their assertions on a bus-less fake, and the tests
that only made sense for the old transport's in-memory holding go with it.

internal/broker/broker_test.go

@@ -194,16 +194,3 @@ func TestTheAddressPortFollowsThePortTwin(t *testing.T) {
 		t.Fatalf("the address is %q; the node put the bus on 5679", b.Address)
 	}
 }
-
-func TestTheManagementPortFollowsThePortTwin(t *testing.T) {
-	t.Setenv(ManagementVar, "http://guest:guest@127.0.0.1:15672")
-	t.Setenv(ManagementVar+"_FILE", "")
-	t.Setenv(ManagementVar+"_PORT", "15673")
-	m, err := ManagementFromEnvironment()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if m.base.Host != "127.0.0.1:15673" {
-		t.Fatalf("the management API is at %q; the node put it on 15673", m.base.Host)
-	}
-}