[REF] l10n_fr_account: host custom migration scripts in a dedicated `--upgrade-path`

Custom migration scripts for a core module used to require copying the
whole module into ``versions/18.0/addons/`` so its ``migrations/`` folder
would be picked up. Because the migration container mounts that copy with
priority (``--addons-path=mig,addons``) and ``get_module_path`` returns the
first match, the copy fully shadowed the core module — dragging along its
entire data/models just to carry one script.

Instead, inject the scripts through a dedicated OpenUpgrade ``upgrade_path``:

- New ``versions/18.0/scripts/l10n_fr_account/18.0.2.2/`` holding
  ``pre-migration-0k-fix-orphan-expressions.py`` (converted to the
  ``@openupgrade.migrate()`` / ``migrate(env, version)`` convention) and
  ``post-migration-0k-vat-box25.py`` + ``noupdate_changes.xml`` that reapply
  the box 25 VAT-report customization via ``openupgrade.load_data``.
- ``config/compose.yml``: mount it as ``/opt/odoo/auto/upgrade`` for ou18.
- ``versions/18.0/upgrade.sh``: pass
  ``--upgrade-path=/opt/odoo/auto/upgrade,/opt/odoo/auto/addons/openupgrade_scripts/scripts``.
  Odoo appends every path to ``odoo.upgrade.__path__`` and concatenates the
  per-version scripts, so our scripts run IN ADDITION to the native ones;
  the native path is listed explicitly because ``--upgrade-path`` overrides
  ``config['upgrade_path']`` which ``openupgrade_framework`` only sets when empty.

Files are named with a ``-0k-`` marker so they never collide with the native
``pre-migration.py`` / ``post-migration.py``. This removes the need for the
shadowing module copy entirely.

Also ignore ``__pycache__``/``*.pyc``.

versions/18.0/upgrade.sh

@@ -1,4 +1,11 @@
 #!/bin/bash
 set -euo pipefail
 
-run_compose run -p 8018:8069 ou18 --config=/opt/odoo/auto/odoo.conf --stop-after-init -u all --workers 0 --log-level=debug --max-cron-threads=0 --limit-time-real=10000 --database=ou18 --load=base,web,openupgrade_framework
+# --upgrade-path lists BOTH our custom migration scripts and OpenUpgrade's
+# native ones. Passing --upgrade-path overrides config['upgrade_path'], and
+# openupgrade_framework only sets that default when it is empty; so we must
+# include the native openupgrade_scripts/scripts path explicitly, otherwise the
+# native migration scripts would no longer run. Odoo appends every listed path
+# to odoo.upgrade.__path__ and concatenates (does not override) the scripts
+# found per module/version, so our script runs IN ADDITION to the native ones.
+run_compose run -p 8018:8069 ou18 --config=/opt/odoo/auto/odoo.conf --stop-after-init -u all --workers 0 --log-level=debug --max-cron-threads=0 --limit-time-real=10000 --database=ou18 --load=base,web,openupgrade_framework --addons-path=/opt/odoo/auto/mig,/opt/odoo/auto/addons --upgrade-path=/opt/odoo/auto/upgrade,/opt/odoo/auto/addons/openupgrade_scripts/scripts