Ensure workorder sequence is applied on new workorders

Test sequence is applied for multiple operations
Rewrite _reset_work_order_sequence in a more pythonic way
Change _order of mrp.workorder to use sequence
Set sequence on existing workorders after module install

mrp_workorder_sequence/hooks.py

@@ -0,0 +1,11 @@
+# Copyright 2022 Camptocamp SA
+# License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl)
+from odoo import SUPERUSER_ID, api, tools
+
+
+def post_init_hook(cr, registry):
+    env = api.Environment(cr, SUPERUSER_ID, {})
+    all_workorders = env["mrp.workorder"].search([], order="production_id ASC, id ASC")
+    for _, workorders in tools.groupby(all_workorders, lambda w: w.production_id):
+        for seq, wo in enumerate(workorders, 1):
+            wo.sequence = seq