perf: index for item-sh on repost item valuation

Item-WH based reposting requires querying existing similar repost.
Assuming there is only 1 max extra entry with same params just indexing
item-WH is sufficient to speed up the query.

(cherry picked from commit a5a8c9104f)

erpnext/stock/doctype/repost_item_valuation/repost_item_valuation.json

@@ -177,7 +177,7 @@
  "index_web_pages_for_search": 1,
  "is_submittable": 1,
  "links": [],
- "modified": "2021-11-18 02:18:10.524560",
+ "modified": "2021-11-24 02:18:10.524560",
  "modified_by": "Administrator",
  "module": "Stock",
  "name": "Repost Item Valuation",
@@ -228,4 +228,4 @@
  ],
  "sort_field": "modified",
  "sort_order": "DESC"
-}
+}

erpnext/stock/doctype/repost_item_valuation/repost_item_valuation.py

@@ -60,6 +60,11 @@ class RepostItemValuation(Document):
 		frappe.enqueue(repost, timeout=1800, queue='long',
 			job_name='repost_sle', now=True, doc=self)
 
+
+def on_doctype_update():
+	frappe.db.add_index("Repost Item Valuation", ["warehouse", "item_code"], "item_warehouse")
+
+
 def repost(doc):
 	try:
 		if not frappe.db.exists("Repost Item Valuation", doc.name):