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?