Rewrite and cleanup HACL* `blake2module.c`

[picnixz]

Some parts of blake2module.c have duplicated bits, and most of the file has lines exceeding 100 characters. I wouldn't bother about lines exceeding 80 characters, but here we're talking about lines that exceed my (laptop) screen.

When we switched from our implementation of BLAKE-2 to the HACL*, I mentioned cleaning it up, but I forgot about this.

Linked PRs

• gh-135004: rewrite and cleanup blake2module.c #135006