[modeling utils] revamp from_pretrained(..., low_cpu_mem_usage=True) + tests (#16657)

* add low_cpu_mem_usage tests

* wip: revamping

* wip

* install /usr/bin/time

* wip

* cleanup

* cleanup

* cleanup

* cleanup

* cleanup

* fix assert

* put the wrapper back

* cleanup; switch to bert-base-cased

* Trigger CI

* Trigger CI

.circleci/config.yml

@@ -217,7 +217,7 @@ jobs:
                   keys:
                       - v0.4-torch-{{ checksum "setup.py" }}
                       - v0.4-{{ checksum "setup.py" }}
-            - run: sudo apt-get -y update && sudo apt-get install -y libsndfile1-dev espeak-ng
+            - run: sudo apt-get -y update && sudo apt-get install -y libsndfile1-dev espeak-ng time
             - run: pip install --upgrade pip
             - run: pip install .[sklearn,torch,testing,sentencepiece,torch-speech,vision,timm]
             - run: pip install torch-scatter -f https://pytorch-geometric.com/whl/torch-1.11.0+cpu.html