models.py -> loaders/ module refactor (#2680)

* models.py -> loaders/ module refactor

* refactor ModelLoader class

* plugin manager changes

* circular import fix

* pytest

* pytest

* minor improvements

* fix

* minor changes

* fix test

* remove dead code

* coderabbit comments

* lint

* fix

* coderabbit suggestion I liked

* more coderabbit

* review comments, yak shaving

* lint

* updating in light of SP ctx manager changes

* review comment

* review comment 2

tests/test_tokenizers.py

@@ -6,8 +6,8 @@ import unittest
 
 import pytest
 
+from axolotl.loaders import load_tokenizer
 from axolotl.utils.dict import DictDefault
-from axolotl.utils.models import load_tokenizer
 
 from tests.hf_offline_utils import enable_hf_offline