ModernBert: reuse GemmaRotaryEmbedding via modular + Integration tests (#35459)
* Introduce 5 integration tests for the 4 model classes + torch export
* ModernBert: reuse GemmaRotaryEmbedding via modular
* Revert #35589, keep rope_kwargs; rely on them in modular_modernbert
* Revert "Revert #35589, keep rope_kwargs; rely on them in modular_modernbert"
This reverts commit 11b44b9ee83e199cbfb7c5ba2d11f7a7fdbba2d3.
* Don't set rope_kwargs; override 'self.rope_init_fn' call instead