Add FlaxCLIPTextModelWithProjection (#25254)

* Add FlaxClipTextModelWithProjection

This is necessary to support the Flax port of Stable Diffusion XL: fb6d705fb5/text_encoder_2/config.json (L3)

Co-authored-by: Martin Müller <martin.muller.me@gmail.com>
Co-authored-by: Juan Acevedo <juancevedo@gmail.com>

* Use FlaxCLIPTextModelOutput

* make fix-copies again

* Apply suggestions from code review

Co-authored-by: Sanchit Gandhi <93869735+sanchit-gandhi@users.noreply.github.com>

* Use `return_dict` for consistency with other uses.

Co-authored-by: Sanchit Gandhi <93869735+sanchit-gandhi@users.noreply.github.com>

* Fix docstring example.

* Add new model to FlaxCLIPTextModelTest

* Add to IGNORE_NON_AUTO_CONFIGURED list

* Fix naming convention.

---------

Co-authored-by: Martin Müller <martin.muller.me@gmail.com>
Co-authored-by: Juan Acevedo <juancevedo@gmail.com>
Co-authored-by: Sanchit Gandhi <93869735+sanchit-gandhi@users.noreply.github.com>

docs/source/en/model_doc/clip.md

@@ -184,6 +184,11 @@ The resource should ideally demonstrate something new instead of duplicating an
 [[autodoc]] FlaxCLIPTextModel
     - __call__
 
+## FlaxCLIPTextModelWithProjection
+
+[[autodoc]] FlaxCLIPTextModelWithProjection
+    - __call__
+
 ## FlaxCLIPVisionModel
 
 [[autodoc]] FlaxCLIPVisionModel