Add Neighborhood Attention Transformer (NAT) and Dilated NAT (DiNAT) models (#20219)

* Add DiNAT

* Adds DiNAT + tests

* Minor fixes

* Added HF model

* Add natten to dependencies.

* Cleanup

* Minor fixup

* Reformat

* Optional NATTEN import.

* Reformat & add doc to _toctree

* Reformat (finally)

* Dummy objects for DiNAT

* Add NAT + minor changes

Adds NAT as its own independent model + docs, tests
Adds NATTEN to ext deps to ensure ci picks it up.

* Remove natten from `all` and `dev-torch` deps, add manual pip install to ci tests

* Minor fixes.

* Fix READMEs.

* Requested changes to docs + minor fixes.

* Requested changes.

* Add NAT/DiNAT tests to layoutlm_job

* Correction to Dinat doc.

* Requested changes.

setup.py

@@ -125,6 +125,7 @@ _deps = [
     "jieba",
     "kenlm",
     "nltk",
+    "natten>=0.14.4",
     "numpy>=1.17",
     "onnxconverter-common",
     "onnxruntime-tools>=1.4.2",
@@ -283,6 +284,7 @@ extras["tf-speech"] = extras["audio"]
 extras["flax-speech"] = extras["audio"]
 extras["vision"] = deps_list("Pillow")
 extras["timm"] = deps_list("timm")
+extras["natten"] = deps_list("natten")
 extras["codecarbon"] = deps_list("codecarbon")