Add basic tuple and value fetching from queries.

Add safeties for =destroy hooks.

FossilOrigin-Name: 2fae5297a0d0598cc3580777688b4f4307de008d4f379d2fb224c8a74cb9b708

tests/queries/t_knows_if_there_are_waiting_tuples.nim

@@ -0,0 +1,24 @@
+# vim: set et sta sw=4 ts=4 :
+
+import kuzu
+
+let db = newKuzuDatabase()
+let conn = db.connect
+
+var q = conn.query( "CREATE NODE TABLE Doop ( id SERIAL, thing STRING, PRIMARY KEY(id) )" )
+assert typeOf( q ) is KuzuQueryResult
+
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+assert q.num_tuples == 0
+assert q.hasNext == false
+
+q = conn.query( "CREATE (d:Doop {thing: 'okay!'})" )
+q = conn.query( "MATCH (d:Doop) RETURN d.thing" )
+assert q.num_tuples == 1
+assert q.hasNext == true
+
+discard $q  # consume the tuple result
+
+assert q.num_tuples == 1
+assert q.hasNext == false
+