Set permissions after streaming unzip (#1151)
## Summary
When we migrated to an "unzip while we stream" solution, we lost the
logic to set permissions on the extracted files, so executables in
wheels were no longer executable. It turns out this is a little tricky,
since the permissions metadata is in the central directory at the _end_
of the zip file, and the async ZIP reader explicitly stops iteration
once it hits the central directory. (Specifically, it goes 4 bytes into
the central directory, since it sees the 4-byte signature header and
then stops.)
So, to solve that, I've added a `CentralDirectoryReader` that continues
where that iterator left off. This required forking the async zip crate:
https://github.com/charliermarsh/rs-async-zip/pull/1. It took a lot of
fiddling but I'm quite confident in the code now, especially since the
async zip crate validates the signature kind on every read.
The central directory is typically quite small (even for the Zig wheel,
which is enormous, it's just around 1MB), so I don't expect this to have
a high cost.
Closes https://github.com/astral-sh/puffin/issues/1148.
