Changes in preparation of Zig 0.15.0

[deckarep]

While I haven't been following closely, there have been some changes with respect to conventions within the Zig standard lib that I'd like to probably implement in this repo.

• Audit the latest Zig conventions, idioms for Zig 0.15.0 to have this Set match such changes
• One example I can think of: It seems like the managed variants of some collections will be deprecated? Confirm.
• Another big one is that the GeneralPurposeAllocator has been renamed to DebugAllocator and is no longer considered to be a Release quality allocator due to its performance cost.
• What else?

[PauSolerValades]

Zig is indeed dropping the managed variants of most containers in the std (https://codeberg.org/ziglang/zig/issues/31220). To use your library according to new standards I've rewritten the Hash implementation following the same philosophy in my fork of your repo (https://github.com/PauSolerValades/set). If you are interested I can PR, but wanted to ask first!

[deckarep]

Yes I welcome the new contributions. Feel free to send the PR and I'll look it over in the coming days.

Cheers!