[12.0][ENH] excel_import_export, faster export

Previously export is slow on large number of rows.
This fix ensure that sheet.insert_rows is called only once for all rows,
instead of insert 1 row for every rows

excel_import_export/models/xlsx_export.py

@@ -200,9 +200,7 @@ class XLSXExport(models.AbstractModel):
                 # Insert rows to preserve total line
                 if not rows_inserted:
                     rows_inserted = True
-                    if row_count > 1:
-                        for _x in range(row_count-1):
-                            st.insert_rows(row+1)
+                    st.insert_rows(row+1, amount=row_count-1)
                 # --
                 for (row_val, style) in vals[field]:
                     new_row = row + i

excel_import_export/readme/HISTORY.rst

@@ -1,3 +1,8 @@
+12.0.1.0.5 (2019-12-19)
+~~~~~~~~~~~~~~~~~~~~~~~
+
+* Speed up export when dealing with many rows
+
 12.0.1.0.4 (2019-08-28)
 ~~~~~~~~~~~~~~~~~~~~~~~