Add DETR (#11653)

* Squash all commits of modeling_detr_v7 branch into one

* Improve docs

* Fix tests

* Style

* Improve docs some more and fix most tests

* Fix slow tests of ViT, DeiT and DETR

* Improve replacement of batch norm

* Restructure timm backbone forward

* Make DetrForSegmentation support any timm backbone

* Fix name of output

* Address most comments by @LysandreJik

* Give better names for variables

* Conditional imports + timm in setup.py

* Address additional comments by @sgugger

* Make style, add require_timm and require_vision to testsé

* Remove train_backbone attribute of DetrConfig, add methods to freeze/unfreeze backbone

* Add png files to fixtures

* Fix type hint

* Add timm to workflows

* Add `BatchNorm2d` to the weight initialization

* Fix retain_grad test

* Replace model checkpoints by Facebook namespace

* Fix name of checkpoint in test

* Add user-friendly message when scipy is not available

* Address most comments by @patrickvonplaten

* Remove return_intermediate_layers attribute of DetrConfig and simplify Joiner

* Better initialization

* Scipy is necessary to get sklearn metrics

* Rename TimmBackbone to DetrTimmConvEncoder and rename DetrJoiner to DetrConvModel

* Make style

* Improve docs and add 2 community notebooks

Co-authored-by: Lysandre <lysandre.debut@reseau.eseo.fr>

setup.py

@@ -142,6 +142,7 @@ _deps = [
     "tensorflow-cpu>=2.3",
     "tensorflow>=2.3",
     "timeout-decorator",
+    "timm",
     "tokenizers>=0.10.1,<0.11",
     "torch>=1.0",
     "torchaudio",
@@ -249,6 +250,7 @@ extras["integrations"] = extras["optuna"] + extras["ray"]
 extras["serving"] = deps_list("pydantic", "uvicorn", "fastapi", "starlette")
 extras["speech"] = deps_list("soundfile", "torchaudio")
 extras["vision"] = deps_list("Pillow")
+extras["timm"] = deps_list("timm")
 
 extras["sentencepiece"] = deps_list("sentencepiece", "protobuf")
 extras["testing"] = (
@@ -270,6 +272,7 @@ extras["all"] = (
     + extras["speech"]
     + extras["vision"]
     + extras["integrations"]
+    + extras["timm"]
 )
 
 extras["docs_specific"] = deps_list(