Native AOT support for NET8.0 and above.

[Samael7777]

Transition to import code generation using CsWin32 without marshaling. Native AOT support for NET8.0 and above.

[emoacht]

Thank you for the PR.
Native AOT is great. CsWin32 is generally useful for new implementation but it is not much in the case of alreadly completed project.

That said, after some consideration, I have concluded that I cannot merge this PR.

First, the commit of this PR is too big for review.

Second, from a quick glance at a small portion of this commit, the changes seem to mix at least four different objectives and it is hard to tell which changes are essential to which.

• Migrating to .NET 8.0
• Enabling Native AOT
• Adoption of CsWin32
• Unclear rationale (file splitting and relocation, avoidance of file-scoped namespaces, etc.)

Combining these makes this commit practically unreviewable. Mergining it as-is would comprimise the long-term maintanablity.