backporting `@atomic` macro from julia-1.12

[kalmarek]

pull: JuliaLang/julia#54707
It requires GenericMemory which landed only in julia-1.11, so the backport will be only limited in scope.

@vchuravy how do you envision such a backport?

[vchuravy]

So one idea would be to "simply" @static if and have Atomix just re-export @atomic from Julia Base.

This will likely cause issue with Atomix usage in KernelAbstractions and the GPU backends. One would also need to make sure that the semantics of @atomic match between Base and Atomix.

Alternativly replace the implementation for the CPU in Atomix on 1.12 with direct calls to the Memory related pieces.