Does not build on MacOS due to `io_uring`

Currently io_uring is not gated behind a feature. This is causing Mac OS builds to fail. I suspect that normally Liquid Cache is meant to run on Linux hardware, but, for a good developer experience it would be desirable to run on Mac OS. Also, not all linux kernel versions support io_uring. Running cargo tree shows that a good portion of the project relies on it without any form of feature gate or platform specification.

> cargo tree -i io-uring
io-uring v0.7.11
└── t4 v0.1.3
    ├── liquid-cache v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/core)
    │   ├── liquid-cache-benchmarks v0.0.0 (/Users/devan/Documents/OSS/liquid-cache/benchmark)
    │   ├── liquid-cache-datafusion v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion)
    │   │   ├── liquid-cache-benchmarks v0.0.0 (/Users/devan/Documents/OSS/liquid-cache/benchmark)
    │   │   ├── liquid-cache-datafusion-local v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion-local)
    │   │   │   ├── examples v0.0.0 (/Users/devan/Documents/OSS/liquid-cache/examples)
    │   │   │   └── liquid-cache-benchmarks v0.0.0 (/Users/devan/Documents/OSS/liquid-cache/benchmark)
    │   │   └── liquid-cache-datafusion-server v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion-server)
    │   │       ├── examples v0.0.0 (/Users/devan/Documents/OSS/liquid-cache/examples)
    │   │       └── liquid-cache-benchmarks v0.0.0 (/Users/devan/Documents/OSS/liquid-cache/benchmark)
    │   ├── liquid-cache-datafusion-local v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion-local) (*)
    │   ├── liquid-cache-datafusion-server v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion-server) (*)
    │   └── liquid-cache-fuzz v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/fuzz)
    ├── liquid-cache-datafusion v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion) (*)
    ├── liquid-cache-datafusion-local v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion-local) (*)
    └── liquid-cache-datafusion-server v0.1.12 (/Users/devan/Documents/OSS/liquid-cache/src/datafusion-server) (*)

See: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#platform-specific-dependencies & https://doc.rust-lang.org/cargo/reference/features.html

Inspect the Cargo manifests for liquid-cache and the workspace crates listed by cargo tree -i io-uring, then review Cargo's platform-specific dependency and feature documentation. Run the dependency tree and a macOS build to identify every path pulling in io-uring. Done means the affected macOS builds succeed without compiling io-uring, while supported Linux builds retain the required functionality.