* new USE_GIVEN_LANGUAGE_ORDER setting

* remove use_given_order param and use USE_GIVEN_LANGUAGE_ORDER setting in DateDataParser

* docs for USE_GIVEN_LANGUAGE_ORDER

* fix date order parsing with empty languages or locales

* added empty locales case in docs

* removed use_given_order tests from init date tests

* added USE_GIVEN_LANGUAGE_ORDER tests

* flake8 fix for tests and conf.py

* add mandatory locales or languages when USE_GIVEN_LANGUAGES is set and fixed tests

* Finalize USE_GIVEN_LANGUAGE_ORDER: keep use_given_order, no-op on empty (#770)

Reconcile the rebased work onto current master with the agreed design:

- Keep the public ``use_given_order`` constructor argument (non-breaking);
  the new ``USE_GIVEN_LANGUAGE_ORDER`` setting is OR-ed with it rather than
  replacing it, and also reaches the top-level ``dateparser.parse()``.
- When the setting is True but no languages/locales are given, it is a no-op
  (fall back to the default order) instead of raising.
- Register ``USE_GIVEN_LANGUAGE_ORDER`` in ``check_settings`` so it is a valid
  setting, document it under "Language Order" in docs/settings.rst, and add
  settings-validation and parsing tests.
- Revert the unneeded loader change: DateDataParser already normalizes an
  empty languages list to None.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Serhii A <aserhii@protonmail.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>