Add TensorFlow implementation of EfficientFormer (#22620)

* Add tf code for efficientformer

* Fix return dict bug - return last hidden state after last stage

* Fix corresponding return dict bug

* Override test tol

* Change default values of training to False

* Set training to default False X3

* Rm axis from ln

* Set init in dense projection

* Rm debug stuff

* Make style; all tests pass.

* Modify year to 2023

* Fix attention biases codes

* Update the shape list logic

* Add a batch norm eps config

* Remove extract comments in test files

* Add conditional attn and hidden states return for serving output

* Change channel dim checking logic

* Add exception for withteacher model in training mode

* Revert layer count for now

* Add layer count for conditional layer naming

* Transpose for conv happens only in main layer

* Make tests smaller

* Make style

* Update doc

* Rm from_pt

* Change to actual expect image class label

* Remove stray print in tests

* Update image processor test

* Remove the old serving output logic

* Make style

* Make style

* Complete test

utils/documentation_tests.txt

@@ -82,6 +82,7 @@ src/transformers/models/dpt/modeling_dpt.py
 src/transformers/models/electra/configuration_electra.py
 src/transformers/models/electra/modeling_electra.py
 src/transformers/models/electra/modeling_tf_electra.py
+src/transformers/models/efficientformer/modeling_tf_efficientformer.py
 src/transformers/models/ernie/configuration_ernie.py
 src/transformers/models/ernie_m/configuration_ernie_m.py
 src/transformers/models/ernie_m/modeling_ernie_m.py