Runtime support for Swift Interop in .NET 10

[kotlarmilos]

Overview

This issue is a follow-up to #93631 and tracks the progress of runtime support required for Swift interop in .NET 10. The exact scope of work is defined by the use cases.

Workstream: ABI compatibility

In order to make the .NET ABI compatible with the Swift ABI, we need to address the following:

• Memory management: .NET runtime provides ABI support for memory management compatible with Swift ARC; clear memory ownership.
• Interop between Swift and ObjC: Swift types projected C# can live alongside ObjC without mem leaks.
• Trimming compatible C# bindings
• Runtime:
  • Async support
  • Generics lowering
  • Structs lowering
    • [API Proposal]: New attribute for interop-specific struct concerns #100896
    • [swift interop] Cannot call instance methods with at least one parameter when using SwiftSelf<T>  #107946
    • [Swift Interop] Lowering fixed buffers #107620
    • Add cache that maps structs to computed lowering to eliminate repeated runs of lowering algorithm
  • SwiftSelf<T> support
    • Investigate why ARGLOADA should require a pointer-like type
    • Lower inner type instead of generic
    • Switch SwiftSelf<T> position requirement to last #108547 - CoreCLR
    • Swift interop: TestSelfIsFrozenNonEnregisteredStructWithExtraArgs fails on Mono #108855

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