Remove some more SPI attributes

Author: grynspan

Sources/Overlays/_Testing_CoreGraphics/Attachments/_AttachableImageContainer.swift

@@ -9,7 +9,7 @@
 //
 
 #if SWT_TARGET_OS_APPLE && canImport(CoreGraphics)
-@_spi(Experimental) public import Testing
+public import Testing
 private import CoreGraphics
 
 private import ImageIO

Sources/Testing/Events/Event.swift

@@ -102,7 +102,6 @@ public struct Event: Sendable {
     ///
     /// - Parameters:
     ///   - attachment: The attachment that was created.
-    @_spi(Experimental)
     indirect case valueAttached(_ attachment: Attachment<AnyAttachable>)
 
     /// A test ended.

Sources/Testing/Events/Recorder/Event.Symbol.swift

@@ -44,7 +44,6 @@ extension Event {
     case details
 
     /// The symbol to use when describing an instance of ``Attachment``.
-    @_spi(Experimental)
     case attachment
   }
 }

Sources/Testing/Issues/Issue.swift

@@ -65,7 +65,6 @@ public struct Issue: Sendable {
     ///
     /// - Parameters:
     ///   - error: The error which was associated with this issue.
-    @_spi(Experimental)
     case valueAttachmentFailed(_ error: any Error)
 
     /// An issue occurred due to misuse of the testing library.

Sources/Testing/Running/Configuration.swift

@@ -237,7 +237,6 @@ public struct Configuration: Sendable {
   /// The value of this property must refer to a directory on the local file
   /// system that already exists and which the current user can write to. If it
   /// is a relative path, it is resolved to an absolute path automatically.
-  @_spi(Experimental)
   public var attachmentsPath: String? {
     get {
       _attachmentsPath