Revamp `md5.py` (#8065)

* Add type hints to md5.py

* Rename some vars to snake case

* Specify functions imported from math

* Rename vars and functions to be more descriptive

* Make tests from test function into doctests

* Clarify more var names

* Refactor some MD5 code into preprocess function

* Simplify loop indices in get_block_words

* Add more detailed comments, docs, and doctests

* updating DIRECTORY.md

* updating DIRECTORY.md

* updating DIRECTORY.md

* updating DIRECTORY.md

* updating DIRECTORY.md

* Add type hints to md5.py

* Rename some vars to snake case

* Specify functions imported from math

* Rename vars and functions to be more descriptive

* Make tests from test function into doctests

* Clarify more var names

* Refactor some MD5 code into preprocess function

* Simplify loop indices in get_block_words

* Add more detailed comments, docs, and doctests

* updating DIRECTORY.md

* updating DIRECTORY.md

* updating DIRECTORY.md

* updating DIRECTORY.md

* Convert str types to bytes

* Add tests comparing md5_me to hashlib's md5

* Replace line-break backslashes with parentheses

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