perf: new column posting datetime in SLE to optimize stock ledger related queries

(cherry picked from commit d80ca523a4)

erpnext/patches/v14_0/update_posting_datetime_and_dropped_indexes.py

@@ -0,0 +1,19 @@
+import frappe
+
+
+def execute():
+	frappe.db.sql(
+		"""
+		UPDATE `tabStock Ledger Entry`
+			SET posting_datetime = timestamp(posting_date, posting_time)
+	"""
+	)
+
+	drop_indexes()
+
+
+def drop_indexes():
+	if not frappe.db.has_index("tabStock Ledger Entry", "posting_sort_index"):
+		return
+
+	frappe.db.sql_ddl("ALTER TABLE `tabStock Ledger Entry` DROP INDEX `posting_sort_index`")