Add explicit initialization for all PlannerGlobal fields

When creating a new PlannerGlobal node in standard_planner(), most
fields are explicitly initialized, but a few are not.  This doesn't
cause any functional issues, as makeNode() zeroes all fields by
default.  However, the inconsistency is undesirable from a clarity and
maintenance perspective.

This patch explicitly initializes the remaining fields to improve
consistency and readability.

Author: Richard Guo <guofenglinux@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Discussion: https://postgr.es/m/CAMbWs4-TgQHNOiouqGcuHoBqbJjWyx4UxGKxUY3FrF4trGbcPA@mail.gmail.com

src/backend/optimizer/plan/planner.c

@@ -326,10 +326,14 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
 	glob->subroots = NIL;
 	glob->rewindPlanIDs = NULL;
 	glob->finalrtable = NIL;
+	glob->allRelids = NULL;
+	glob->prunableRelids = NULL;
 	glob->finalrteperminfos = NIL;
 	glob->finalrowmarks = NIL;
 	glob->resultRelations = NIL;
+	glob->firstResultRels = NIL;
 	glob->appendRelations = NIL;
+	glob->partPruneInfos = NIL;
 	glob->relationOids = NIL;
 	glob->invalItems = NIL;
 	glob->paramExecTypes = NIL;
@@ -338,6 +342,7 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
 	glob->lastPlanNodeId = 0;
 	glob->transientPlan = false;
 	glob->dependsOnRole = false;
+	glob->partition_directory = NULL;
 
 	/*
 	 * Assess whether it's feasible to use parallel mode for this query. We