[IMP] account_ebics - Add unit tests

Add 97 tests:

- account_ebics: order numbers, camt and CFONB split per account,
  journal lookup, duplicate statements, download and upload wizards,
  key initialisation (INI/HIA/HPB), passphrase change, admin orders.
- account_ebics_batch: scheduled import, import log, reprocess.
- account_ebics_payment_order / account_ebics_batch_payment: upload of
  the payment file and link to the payment document.
- account_ebics_statement_import_test (new, test-only, not to install
  in production): installs the OCA camt and CFONB parsers in CI and
  runs the end-to-end statement import.

The bank is simulated by patching ebics.xfer._setup_client, or the
fintech client classes for the key initialisation; keys, certificates
and the INI letter are real, created in a temporary directory.

.github/workflows/test.yml

@@ -50,7 +50,7 @@ jobs:
             name: test with Odoo Community
             odoo_enterprise : 0
             exclude_modules : "account_asset"
-            skip: "account_ebics_batch_payment,account_ebics_oe"
+            skip: "account_ebics_batch_payment,account_ebics_oe,account_ebics_oe_statement_import_test"
           - container: ghcr.io/noviat-ci/odoo-ci:18.0-stable
             name: test with Odoo Enterprise
             odoo_enterprise : 1