Replace publicroomsapi with a combination of clientapi/roomserver/currentstateserver (#1174)

* Use content_value instead of membership

* Fix build

* Replace publicroomsapi with a combination of clientapi/roomserver/currentstateserver

- All public rooms paths are now handled by clientapi
- Requests to (un)publish rooms are sent to the roomserver via `PerformPublish`
  which are stored in a new `published_table.go`
- Requests for public rooms are handled in clientapi by:
    * Fetch all room IDs which are published using `QueryPublishedRooms` on the roomserver.
    * Apply pagination parameters to the slice.
    * Do a `QueryBulkStateContent` request to the currentstateserver to pull out
      required state event *content* (not entire events).
    * Aggregate and return the chunk.

Mostly but not fully implemented (DB queries on currentstateserver are missing)

* Fix pq query

* Make postgres work

* Make sqlite work

* Fix tests

* Unbreak pagination tests

* Linting

clientapi/routing/directory_public_test.go

@@ -0,0 +1,48 @@
+package routing
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestSliceInto(t *testing.T) {
+	slice := []string{"a", "b", "c", "d", "e", "f", "g"}
+	limit := int16(3)
+	testCases := []struct {
+		since      int64
+		wantPrev   int
+		wantNext   int
+		wantSubset []string
+	}{
+		{
+			since:      0,
+			wantPrev:   -1,
+			wantNext:   3,
+			wantSubset: slice[0:3],
+		},
+		{
+			since:      3,
+			wantPrev:   0,
+			wantNext:   6,
+			wantSubset: slice[3:6],
+		},
+		{
+			since:      6,
+			wantPrev:   3,
+			wantNext:   -1,
+			wantSubset: slice[6:7],
+		},
+	}
+	for _, tc := range testCases {
+		subset, prev, next := sliceInto(slice, tc.since, limit)
+		if !reflect.DeepEqual(subset, tc.wantSubset) {
+			t.Errorf("returned subset is wrong, got %v want %v", subset, tc.wantSubset)
+		}
+		if prev != tc.wantPrev {
+			t.Errorf("returned prev is wrong, got %d want %d", prev, tc.wantPrev)
+		}
+		if next != tc.wantNext {
+			t.Errorf("returned next is wrong, got %d want %d", next, tc.wantNext)
+		}
+	}
+}