Revamp md5.py

[tianyizheng02]

Describe your change:

Revamped hashes/md5.py:

• Added type hints to all functions
• Added doctests to all functions
• Greatly expanded documentation for all functions
• Added input validation to some functions as needed
• Added reference to the Wikipedia article that the implementation is based on
• Renamed some variables and functions to clarify their usage
• Minor refactoring for clarity

There's a lot in this PR, so let me know if anything else should be changed or if any existing changes should be reverted

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the commit message contains Fixes: #{$ISSUE_NO}.

[cclauss]

Please use https://docs.python.org/3/library/struct.html to do the endian conversations or at least use struct in the doctests for to_little_endian().

[tianyizheng02]

Admittedly I'm not that familiar with the struct module, but I'm not sure how to make it work with the to_little_endian() function.

To me, the problem is that the original function rearrange() doesn't actually convert strings to little-endian. Instead, it treats 32-char string inputs as if they were 32-bit bit strings, with each char as a single "bit". It then restructures the input in an "little-endian fashion": the 8 least significant "bits" come first, followed by the 8 next least significant "bits", etc. Thus it looks little-endian if you squint hard enough.

Since the inputs to rearrange()/to_little_endian() are being restructured in units far larger than a byte, I'm not sure if the struct module would work here, unless I'm misunderstanding how the module works.

[cclauss]

The ruff errors should go away if you rebase.

[cclauss]

For me, there are two things that I see missing...

1. Tests comparing against hashlib.md5(msg).hexdigest()
2. Hashes are usually calculated from messages that are bytes, not str so md5_me() should take bytes, not str.

    >>> import hashlib
    >>> from strings import ascii_letters
    >>> msgs = (b"", ascii_letters.encode("utf-8"), "Üñîçø∂é".encode("utf-8"),
    ...         b"The quick brown fox jumps over the lazy dog.")
    >>> all(md5_me(bytes_msg) == hashlib.md5(bytes_msg).hexdigest() for bytes_msg in msgs)
    True

[cclauss]

Nice!!