At the moment, 7zip files are generating memory issues and even OOM
errors on user installations. This is because the current stable release
of `py7zr` does not support decompression streaming, and RomM needs to
decompress the each 7zip file in the library into memory to be able to
calculate hashes.
This change introduces a `py7zr` fork I created to have a stable commit
SHA to refer to in case upstream gets any forced pushes. It includes the
contents of the pull request the `py7zr` creator is working on to
support decompression streaming [1].
The way decompression streaming is implemented in `py7zr` is different
than the other compression utilities. Instead of being able to provide a
`bytes` iterator, we need to provide a `Py7zIO` implementation that
will call a callback on each read and write operation.
[1] https://github.com/miurahr/py7zr/pull/620
