Commit to main--missing @_spi attributes on some symbols breaking the build

Author: grynspan

Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageWrapper+AttachableWrapper.swift

@@ -39,6 +39,7 @@ private import UniformTypeIdentifiers
 ///    useful.)
 
 @available(_uttypesAPI, *)
+@_spi(Experimental)
 extension _AttachableImageWrapper: Attachable, AttachableWrapper where Image: AttachableAsCGImage {
   public func withUnsafeBytes<R>(for attachment: borrowing Attachment<_AttachableImageWrapper>, _ body: (UnsafeRawBufferPointer) throws -> R) throws -> R {
     let data = NSMutableData()

Sources/Overlays/_Testing_WinSDK/Attachments/_AttachableImageWrapper+AttachableWrapper.swift

@@ -12,6 +12,7 @@
 @_spi(Experimental) public import Testing
 private import WinSDK
 
+@_spi(Experimental)
 extension _AttachableImageWrapper: Attachable, AttachableWrapper where Image: AttachableAsIWICBitmapSource {
   public func withUnsafeBytes<R>(for attachment: borrowing Attachment<_AttachableImageWrapper>, _ body: (UnsafeRawBufferPointer) throws -> R) throws -> R {
     // Create an in-memory stream to write the image data to. Note that Windows