[Wav2Vec2] Rename model's feature extractor to feature encoder (#14959)

* rename classes

* clean up more namings

* remove bogus file

* Apply suggestions from code review

* Apply suggestions from code review

* replace more names

* more regex replace

* make style

* correct

* correct more

* make style

* finish

* correct more in wav2vec2

* make style

* improve freeze_extractor

* add aliases

* add tf aliases

examples/pytorch/speech-recognition/README.md

@@ -78,7 +78,7 @@ python run_speech_recognition_ctc.py \
 	--eval_steps="100" \
 	--layerdrop="0.0" \
 	--save_total_limit="3" \
-	--freeze_feature_extractor \
+	--freeze_feature_encoder \
 	--gradient_checkpointing \
 	--chars_to_ignore , ? . ! - \; \: \" “ % ‘ ” <20> \
 	--fp16 \
@@ -113,7 +113,7 @@ python -m torch.distributed.launch \
 	--logging_steps="1" \
 	--layerdrop="0.0" \
 	--save_total_limit="3" \
-	--freeze_feature_extractor \
+	--freeze_feature_encoder \
 	--gradient_checkpointing \
 	--chars_to_ignore , ? . ! - \; \: \" “ % ‘ ” <20> \
 	--fp16 \
@@ -304,7 +304,7 @@ python run_speech_recognition_seq2seq.py \
 	--eval_steps="400" \
 	--logging_steps="10" \
 	--save_total_limit="1" \
-	--freeze_feature_extractor \
+	--freeze_feature_encoder \
 	--gradient_checkpointing \
 	--fp16 \
 	--group_by_length \
@@ -346,7 +346,7 @@ python -m torch.distributed.launch \
 	--eval_steps="400" \
 	--logging_steps="10" \
 	--save_total_limit="1" \
-	--freeze_feature_extractor \
+	--freeze_feature_encoder \
 	--gradient_checkpointing \
 	--fp16 \
 	--group_by_length \