Add @_unavailableInEmbedded where appropriate

Author: grynspan

Sources/Testing/Attachments/Images/AttachableImageFormat.swift

@@ -30,6 +30,7 @@
 ///   @Available(Swift, introduced: 6.3)
 /// }
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 @available(_uttypesAPI, *)
@@ -79,6 +80,7 @@ public struct AttachableImageFormat: Sendable {
 // MARK: -
 
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 @available(_uttypesAPI, *)

Sources/Testing/Attachments/Images/Attachment+_AttachableAsImage.swift

@@ -9,6 +9,7 @@
 //
 
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 @available(_uttypesAPI, *)
@@ -101,6 +102,7 @@ extension Attachment {
 
 @_spi(Experimental) // STOP: not part of ST-0014
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 @available(_uttypesAPI, *)

Sources/Testing/Attachments/Images/ImageAttachmentError.swift

@@ -12,6 +12,7 @@ private import _TestingInternals
 
 /// A type representing an error that can occur when attaching an image.
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 package enum ImageAttachmentError: Error {
@@ -43,6 +44,7 @@ package enum ImageAttachmentError: Error {
 }
 
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 extension ImageAttachmentError: CustomStringConvertible {

Sources/Testing/Attachments/Images/_AttachableAsImage.swift

@@ -27,6 +27,7 @@
 ///   that we don't need to underscore its name.
 /// }
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 @available(_uttypesAPI, *)

Sources/Testing/Attachments/Images/_AttachableImageWrapper.swift

@@ -19,6 +19,7 @@
 /// | iOS, watchOS, tvOS, and visionOS | [`CGImage`](https://developer.apple.com/documentation/coregraphics/cgimage), [`CIImage`](https://developer.apple.com/documentation/coreimage/ciimage), [`UIImage`](https://developer.apple.com/documentation/uikit/uiimage) |
 /// | Windows | [`HBITMAP`](https://learn.microsoft.com/en-us/windows/win32/gdi/bitmaps), [`HICON`](https://learn.microsoft.com/en-us/windows/win32/menurc/icons), [`IWICBitmapSource`](https://learn.microsoft.com/en-us/windows/win32/api/wincodec/nn-wincodec-iwicbitmapsource) (including its subclasses declared by Windows Imaging Component) |
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 @available(_uttypesAPI, *)
@@ -40,6 +41,7 @@ public final class _AttachableImageWrapper<Image>: Sendable where Image: _Attach
 }
 
 #if SWT_NO_IMAGE_ATTACHMENTS
+@_unavailableInEmbedded
 @available(*, unavailable, message: "Image attachments are not available on this platform.")
 #endif
 @available(_uttypesAPI, *)