Cast pg_stat_progress_cluster.cluster_index_relid to oid

It's tracked internally as bigint, but when presented to the user it
should be oid.

doc/src/sgml/monitoring.sgml

@@ -3937,7 +3937,7 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
     </row>
     <row>
      <entry><structfield>cluster_index_relid</structfield></entry>
-     <entry><type>bigint</type></entry>
+     <entry><type>oid</type></entry>
      <entry>
        If the table is being scanned using an index, this is the OID of the
        index being used; otherwise, it is zero.

src/backend/catalog/system_views.sql

@@ -933,7 +933,7 @@ CREATE VIEW pg_stat_progress_cluster AS
                       WHEN 6 THEN 'rebuilding index'
                       WHEN 7 THEN 'performing final cleanup'
                       END AS phase,
-        S.param3 AS cluster_index_relid,
+        CAST(S.param3 AS oid) AS cluster_index_relid,
         S.param4 AS heap_tuples_scanned,
         S.param5 AS heap_tuples_written,
         S.param6 AS heap_blks_total,

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201904051
+#define CATALOG_VERSION_NO	201904071
 
 #endif

src/test/regress/expected/rules.out

@@ -1855,7 +1855,7 @@ pg_stat_progress_cluster| SELECT s.pid,
             WHEN 7 THEN 'performing final cleanup'::text
             ELSE NULL::text
         END AS phase,
-    s.param3 AS cluster_index_relid,
+    (s.param3)::oid AS cluster_index_relid,
     s.param4 AS heap_tuples_scanned,
     s.param5 AS heap_tuples_written,
     s.param6 AS heap_blks_total,