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

setup/mscs/msc2836/msc2836_test.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/matrix-org/dendrite/internal/hooks"
 	"github.com/matrix-org/dendrite/internal/httputil"
+	"github.com/matrix-org/dendrite/internal/sqlutil"
 	roomserver "github.com/matrix-org/dendrite/roomserver/api"
 	"github.com/matrix-org/dendrite/setup/base"
 	"github.com/matrix-org/dendrite/setup/config"
@@ -554,10 +555,11 @@ func injectEvents(t *testing.T, userAPI userapi.UserInternalAPI, rsAPI roomserve
 	cfg.Global.ServerName = "localhost"
 	cfg.MSCs.Database.ConnectionString = "file:msc2836_test.db"
 	cfg.MSCs.MSCs = []string{"msc2836"}
+	cm := sqlutil.NewConnectionManager()
 	base := &base.BaseDendrite{
-		Cfg:                    cfg,
-		PublicClientAPIMux:     mux.NewRouter().PathPrefix(httputil.PublicClientPathPrefix).Subrouter(),
-		PublicFederationAPIMux: mux.NewRouter().PathPrefix(httputil.PublicFederationPathPrefix).Subrouter(),
+		Cfg:               cfg,
+		Routers:           httputil.NewRouters(),
+		ConnectionManager: cm,
 	}
 
 	err := msc2836.Enable(base, rsAPI, nil, userAPI, nil)
@@ -567,7 +569,7 @@ func injectEvents(t *testing.T, userAPI userapi.UserInternalAPI, rsAPI roomserve
 	for _, ev := range events {
 		hooks.Run(hooks.KindNewEventPersisted, ev)
 	}
-	return base.PublicClientAPIMux
+	return base.Routers.Client
 }
 
 type fledglingEvent struct {