Adds CLIP to models exportable with ONNX (#18515)

* onnx config for clip

* default opset as 14

* changes from the original repo

* input values order fix

* outputs fix

* remove unused import

* ran make fix-copies

* black format

* review comments: forward ref, import fix, model change revert, .to cleanup

* make style

* formatting fixes

* revert groupvit

* comment for cast to int32

* comment fix

* make .T as .t() for onnx conversion

* ran make fix-copies

* remove unneeded comment

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

* fix copies

* remove comment

Co-authored-by: Sylvain Gugger <35901082+sgugger@users.noreply.github.com>

tests/onnx/test_onnx_v2.py

@@ -185,6 +185,7 @@ PYTORCH_EXPORT_MODELS = {
     ("big-bird", "google/bigbird-roberta-base"),
     ("ibert", "kssteven/ibert-roberta-base"),
     ("camembert", "camembert-base"),
+    ("clip", "openai/clip-vit-base-patch32"),
     ("convbert", "YituTech/conv-bert-base"),
     ("codegen", "Salesforce/codegen-350M-multi"),
     ("deberta", "microsoft/deberta-base"),