Revert "Remove unused wait events."

This reverts commit 671eb8f344. The removed
wait events are used by some extensions and removal of these would force a
recompile of those extensions. We don't want that for released branches.

Discussion: https://postgr.es/m/E1mdOBY-0005j2-QL@gemulon.postgresql.org

doc/src/sgml/monitoring.sgml

@@ -1549,6 +1549,22 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       <entry><literal>WALWrite</literal></entry>
       <entry>Waiting for a write to a WAL file.</entry>
      </row>
+     <row>
+      <entry><literal>LogicalChangesRead</literal></entry>
+      <entry>Waiting for a read from a logical changes file.</entry>
+     </row>
+     <row>
+      <entry><literal>LogicalChangesWrite</literal></entry>
+      <entry>Waiting for a write to a logical changes file.</entry>
+     </row>
+     <row>
+      <entry><literal>LogicalSubxactRead</literal></entry>
+      <entry>Waiting for a read from a logical subxact file.</entry>
+     </row>
+     <row>
+      <entry><literal>LogicalSubxactWrite</literal></entry>
+      <entry>Waiting for a write to a logical subxact file.</entry>
+     </row>
     </tbody>
    </tgroup>
   </table>

src/backend/utils/activity/wait_event.c

@@ -714,6 +714,18 @@ pgstat_get_wait_io(WaitEventIO w)
 		case WAIT_EVENT_WAL_WRITE:
 			event_name = "WALWrite";
 			break;
+		case WAIT_EVENT_LOGICAL_CHANGES_READ:
+			event_name = "LogicalChangesRead";
+			break;
+		case WAIT_EVENT_LOGICAL_CHANGES_WRITE:
+			event_name = "LogicalChangesWrite";
+			break;
+		case WAIT_EVENT_LOGICAL_SUBXACT_READ:
+			event_name = "LogicalSubxactRead";
+			break;
+		case WAIT_EVENT_LOGICAL_SUBXACT_WRITE:
+			event_name = "LogicalSubxactWrite";
+			break;
 
 			/* no default case, so that compiler will warn */
 	}

src/include/utils/wait_event.h

@@ -220,7 +220,11 @@ typedef enum
 	WAIT_EVENT_WAL_READ,
 	WAIT_EVENT_WAL_SYNC,
 	WAIT_EVENT_WAL_SYNC_METHOD_ASSIGN,
-	WAIT_EVENT_WAL_WRITE
+	WAIT_EVENT_WAL_WRITE,
+	WAIT_EVENT_LOGICAL_CHANGES_READ,
+	WAIT_EVENT_LOGICAL_CHANGES_WRITE,
+	WAIT_EVENT_LOGICAL_SUBXACT_READ,
+	WAIT_EVENT_LOGICAL_SUBXACT_WRITE
 } WaitEventIO;