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/link/receive_nats_test.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"io"
+	"log"
 	"os"
 	"sync"
 	"testing"
@@ -120,6 +122,8 @@ func eventually(t *testing.T, what string, is func() bool) {
 
 // A report published by a node reaches the controller, is recorded, and is acknowledged — so the
 // stream does not hold it. A work queue is the check: what is acknowledged leaves it.
+func quiet() *log.Logger { return log.New(io.Discard, "", 0) }
+
 func TestNatsAReportIsHeardAndLeavesTheStream(t *testing.T) {
 	js := aBus(t)
 	store := &counted{}