Use loader notifications for module registration on Windows

[compnerd]

Motivation

Darwin uses a dyld hook for module registration. Windows provides a loader hook for module load notification globally. We should be able to use this to handle metadata registration similar to Darwin on Windows. Doing so would allow us to remove the need for swiftrt.obj (and swiftrtT.obj`).

Proposed solution

Use https://learn.microsoft.com/en-us/windows/win32/devnotes/ldrregisterdllnotification for the notification.

Alternatives considered

No response

Additional information

No response

[al45tair]

I think this sounds easier than it actually is. Those notifications fire before dynamic linking has happened, hence the documentation saying

⚠︎ Warning

It is unsafe for the notification callback to call functions in ANY other module other than itself.

It’s also one of the functions that is marked with

[This function may be changed or removed from Windows without further notice.]

[compnerd]

Yes, it is an internal function. I don't think that the fact that this fires before linking is a big deal. We need to simply retain the knowledge that the module has been loaded.