### Description of the issue/feature this PR addresses
Since February 2026, changes were made in `/tests/common.py` that were probably never tested on anything else than Linux or Mac machines. Since that time, Windows users like me (sorry) are not able to run the Odoo tests anymore on their machine. Because the problem remains to this day, I thought I'd submit a PR to fix this permanently. 
I have not checked versions older than 18, but it seems the problem does not occur in Odoo 19 anymore, as the code in `/tests/common.py` has been greatly improved.

### Current behavior before PR
Running `odoo-bin` with the `--test-enable` flag never works on Windows, because the simple check on [this line](https://github.com/odoo/odoo/blob/18.0/odoo/tests/common.py#L979) fails due to Windows using backslashes instead of forward slashes in file paths.

It results in the following error (and a whole lot more afterwards as a result of that):
```
2026-08-19 10:28:44,868 48604 INFO odoo-local odoo.tests.common: C:\Apps\Python312\Lib\unittest\mock.py:1581:__enter__ setting Users._crypt_context to <function TransactionCase.setUpClass.<locals>._crypt_context at 0x000002C48DD2C540> 
Stack (most recent call last):
  File "C:\Program Files\JetBrains\PyCharm 2024.1.4\plugins\python-ce\helpers\pydev\pydevd.py", line 2391, in <module>
    main()
  File "C:\Program Files\JetBrains\PyCharm 2024.1.4\plugins\python-ce\helpers\pydev\pydevd.py", line 2372, in main
    globals = debugger.run(setup['file'], None, None, is_module)
  File "C:\Program Files\JetBrains\PyCharm 2024.1.4\plugins\python-ce\helpers\pydev\pydevd.py", line 1640, in run
    return self._exec(is_module, entry_point_fn, module_name, file, globals, locals)
  File "C:\Program Files\JetBrains\PyCharm 2024.1.4\plugins\python-ce\helpers\pydev\pydevd.py", line 1647, in _exec
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "C:\Program Files\JetBrains\PyCharm 2024.1.4\plugins\python-ce\helpers\pydev\_pydev_imps\_pydev_execfile.py", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "odoo-bin", line 8, in <module>
    odoo.cli.main()
  File "[REMOVED]\odoo\odoo\cli\command.py", line 76, in main
    o.run(args)
  File "[REMOVED]\odoo\odoo\cli\server.py", line 182, in run
    main(args)
  File "[REMOVED]\odoo\odoo\cli\server.py", line 175, in main
    rc = odoo.service.server.start(preload=preload, stop=stop)
  File "[REMOVED]\odoo\odoo\service\server.py", line 1510, in start
    rc = server.run(preload, stop)
  File "[REMOVED]\odoo\odoo\service\server.py", line 644, in run
    rc = preload_registries(preload)
  File "[REMOVED]\odoo\odoo\service\server.py", line 1414, in preload_registries
    registry = Registry.new(dbname, update_module=update_module)
  File "[REMOVED]\venv\Lib\site-packages\decorator.py", line 232, in fun
    return caller(func, *(extras + args), **kw)
  File "[REMOVED]\odoo\odoo\tools\func.py", line 97, in locked
    return func(inst, *args, **kwargs)
  File "[REMOVED]\odoo\odoo\modules\registry.py", line 118, in new
    odoo.modules.load_modules(registry, force_demo, status, update_module)
  File "[REMOVED]\odoo\odoo\modules\loading.py", line 485, in load_modules
    processed_modules += load_marked_modules(env, graph,
  File "[REMOVED]\odoo\odoo\modules\loading.py", line 365, in load_marked_modules
    loaded, processed = load_module_graph(
  File "[REMOVED]\odoo\odoo\modules\loading.py", line 284, in load_module_graph
    test_results = loader.run_suite(suite, global_report=report)
  File "[REMOVED]\odoo\odoo\tests\loader.py", line 118, in run_suite
    suite(results)
  File "C:\Apps\Python312\Lib\unittest\suite.py", line 84, in __call__
    return self.run(*args, **kwds)
  File "[REMOVED]\odoo\odoo\tests\suite.py", line 43, in run
    self._handleClassSetUp(test, result)
  File "[REMOVED]\odoo\odoo\tests\suite.py", line 175, in _handleClassSetUp
    super()._handleClassSetUp(test, result)
  File "[REMOVED]\odoo\odoo\tests\suite.py", line 65, in _handleClassSetUp
    currentClass.setUpClass()
  File "[REMOVED]\odoo\odoo\tests\common.py", line 1076, in setUpClass
    cls.startClassPatcher(cls._crypt_context_patcher)
  File "[REMOVED]\odoo\odoo\tests\common.py", line 443, in startClassPatcher
    mock = patcher.start()
  File "C:\Apps\Python312\Lib\unittest\mock.py", line 1624, in start
    result = self.__enter__()
  File "C:\Apps\Python312\Lib\unittest\mock.py", line 1581, in __enter__
    setattr(self.target, self.attribute, new_attr)
  File "[REMOVED]\odoo\odoo\tests\common.py", line 985, in metamodel_setattr
    _logger.runbot(
  File "[REMOVED]\odoo\odoo\netsvc.py", line 376, in runbot
    self.log(logging.RUNBOT, message, *args, **kws)
```

### Desired behavior after PR is merged:
The test suite runs without problems on Windows. 
Btw, it would probably be better to use `pathlib` instead as a general improvement for all places in the code where local paths are being handled, but that's out of scope here now.

---
- [x] I confirm I have signed the CLA and read the PR guidelines at www.odoo.com/submit-pr

Forward-Port-Of: odoo/odoo#283210

Currently invoice reports use the label related to the company's country for the partner's vat number, however in the case of latin america countries, a new field l10n_latam_identification_type_id is added to partners that allows the use of different identification types.

This results in invoice reports showing the identification number next to an incorrect label.

This commit fixes the issue for Guatemala and Uruguay by overriding the vat label in
their respective invoice template to match the selected identification type.

Steps to reproduce:
- Install a latam localisation (Uruguay or Guatemala)
- Change company to that country's Company
- Create a partner located in said country, ensure the identification number is set to something else than the default one
- Create an invoice for the partner, confirm it, and then Send it
- In the pdf generated for the invoice you will see that under the partner's address the "vat number" has the wrong label

opw-6087359

related to: https://github.com/odoo/odoo/pull/260159

Forward-Port-Of: odoo/enterprise#122512