Abstract `ProcThreadAttributeList` into its own struct
As extensively discussed in issue #114854, the current implementation of the unstable `windows_process_extensions_raw_attribute` features lacks support for passing a raw pointer.
This PR wants to explore the opportunity to abstract away the `ProcThreadAttributeList` into its own struct to for one improve safety and usability and secondly make it possible to maybe also use it to spawn new threads.
try-job: x86_64-mingw
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