Custom reloptions for table AM

Let table AM define custom reloptions for its tables. This allows specifying
AM-specific parameters by the WITH clause when creating a table.

The reloptions, which could be used outside of table AM, are now extracted
into the CommonRdOptions data structure.  These options could be by decision
of table AM directly specified by a user or calculated in some way.

The new test module test_tam_options evaluates the ability to set up custom
reloptions and calculate fields of CommonRdOptions on their base.

The code may use some parts from prior work by Hao Wu.

Discussion: https://postgr.es/m/CAPpHfdurb9ycV8udYqM%3Do0sPS66PJ4RCBM1g-bBpvzUfogY0EA%40mail.gmail.com
Discussion: https://postgr.es/m/AMUA1wBBBxfc3tKRLLdU64rb.1.1683276279979.Hmail.wuhao%40hashdata.cn
Reviewed-by: Reviewed-by: Pavel Borisov, Matthias van de Meent, Jess Davis

src/backend/access/heap/heapam_handler.c

@@ -23,6 +23,7 @@
 #include "access/heapam.h"
 #include "access/heaptoast.h"
 #include "access/multixact.h"
+#include "access/reloptions.h"
 #include "access/rewriteheap.h"
 #include "access/syncscan.h"
 #include "access/tableam.h"
@@ -2161,6 +2162,17 @@ heapam_relation_toast_am(Relation rel)
 	return rel->rd_rel->relam;
 }
 
+static bytea *
+heapam_reloptions(char relkind, Datum reloptions,
+				  CommonRdOptions *common, bool validate)
+{
+	Assert(relkind == RELKIND_RELATION ||
+		   relkind == RELKIND_TOASTVALUE ||
+		   relkind == RELKIND_MATVIEW);
+
+	return heap_reloptions(relkind, reloptions, common, validate);
+}
+
 
 /* ------------------------------------------------------------------------
  * Planner related callbacks for the heap AM
@@ -2710,6 +2722,7 @@ static const TableAmRoutine heapam_methods = {
 	.relation_needs_toast_table = heapam_relation_needs_toast_table,
 	.relation_toast_am = heapam_relation_toast_am,
 	.relation_fetch_toast_slice = heap_fetch_toast_slice,
+	.reloptions = heapam_reloptions,
 
 	.relation_estimate_size = heapam_estimate_rel_size,