Preparations for removing BaseDendrite (#3016)

Preparations to actually remove/replace `BaseDendrite`.
Quite a few changes:
- SyncAPI accepts an `fulltext.Indexer` interface (fulltext is removed
from `BaseDendrite`)
- Caches are removed from `BaseDendrite`
- Introduces a `Router` struct (likely to change)
  - also fixes #2903
- Introduces a `sqlutil.ConnectionManager`, which should remove
`base.DatabaseConnection` later on
- probably more

federationapi/federationapi_test.go

@@ -10,6 +10,7 @@ import (
 	"testing"
 	"time"
 
+	"github.com/matrix-org/dendrite/internal/caching"
 	"github.com/matrix-org/gomatrix"
 	"github.com/matrix-org/gomatrixserverlib"
 	"github.com/nats-io/nats.go"
@@ -163,6 +164,7 @@ func TestFederationAPIJoinThenKeyUpdate(t *testing.T) {
 
 func testFederationAPIJoinThenKeyUpdate(t *testing.T, dbType test.DBType) {
 	base, close := testrig.CreateBaseDendrite(t, dbType)
+	caches := caching.NewRistrettoCache(base.Cfg.Global.Cache.EstimatedMaxSize, base.Cfg.Global.Cache.MaxAge, caching.DisableMetrics)
 	base.Cfg.FederationAPI.PreferDirectFetch = true
 	base.Cfg.FederationAPI.KeyPerspectives = nil
 	defer close()
@@ -212,7 +214,7 @@ func testFederationAPIJoinThenKeyUpdate(t *testing.T, dbType test.DBType) {
 			},
 		},
 	}
-	fsapi := federationapi.NewInternalAPI(base, fc, rsapi, base.Caches, nil, false)
+	fsapi := federationapi.NewInternalAPI(base, fc, rsapi, caches, nil, false)
 
 	var resp api.PerformJoinResponse
 	fsapi.PerformJoin(context.Background(), &api.PerformJoinRequest{
@@ -278,7 +280,7 @@ func TestRoomsV3URLEscapeDoNot404(t *testing.T) {
 	// TODO: This is pretty fragile, as if anything calls anything on these nils this test will break.
 	// Unfortunately, it makes little sense to instantiate these dependencies when we just want to test routing.
 	federationapi.AddPublicRoutes(b, nil, nil, keyRing, nil, &internal.FederationInternalAPI{}, nil)
-	baseURL, cancel := test.ListenAndServe(t, b.PublicFederationAPIMux, true)
+	baseURL, cancel := test.ListenAndServe(t, b.Routers.Federation, true)
 	defer cancel()
 	serverName := gomatrixserverlib.ServerName(strings.TrimPrefix(baseURL, "https://"))