Add from_raw and into_raw methods to RestoreState.

[reitermarkus]

I have a use case where I need to re-expose _critical_section_1_0_acquire/_critical_section_1_0_release to a shared library that is dynamically loaded.

Specifically, using the elf_loader crate, I need to do this:

unsafe fn _critical_section_1_0_acquire() -> RawRestoreState {
  unsafe { critical_section::acquire().into_raw() }
}

unsafe fn _critical_section_1_0_release(restore_state: RawRestoreState) {
  unsafe { critical_section::release(RestoreState::from_raw(restore_state)) };
}


 SyntheticModule::new(
  "__host",
  [
    SyntheticSymbol::function(
      "_critical_section_1_0_acquire",
      _critical_section_1_0_acquire as *const (),
    ),
    SyntheticSymbol::function(
      "_critical_section_1_0_release",
      _critical_section_1_0_release as *const (),
    ),
  ],
)