Improve error-branches of `hashlib`

[picnixz]

Bug report

Bug description:

While reading the hashlib code, I found some issues in the error branches where the EVP_MD_ctx is not freed upon failure or when we call py_digest_name with a NULL EVP_MD *.

@gpshead Should I consider this as a security issue? (some places might be a security issue since we are leaking some EVP_MD context objects but others are just leaking un-initialized contexts).

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-127667: fix more reference leaks in hashlib #127668
• [3.12] gh-127667: fix memory leaks in hashlib (GH-127668) #130783
• [3.13] gh-127667: fix memory leaks in hashlib (GH-127668) #130784
• gh-127667: refactor and improve _hashopenssl.c error branches #131145
• [3.13] gh-127667: refactor and improve _hashopenssl.c error branches (#131145) #131347
• [3.12] gh-127667: refactor and improve _hashopenssl.c error branches (#131145) #131348