Validate ntco::IoRing structures against kernel definitions, when possible

[mattrm456]

Support for io_uring was added in #24. For a variety of reasons, that implementation does not use the Linux kernel's definitions of io_uring structures, but re-declares them so that the ntco_ioring component is buildable on any Linux kernel version.

When possible, perform compile-time assertions that our reclaration of io_uring structures match the Linux kernels definitions.