Auto merge of #23564 - mmiecz:clipboard-refactoring, r=jdm

Clipboard refactoring

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This PR removes clipboard handling from the constellation. Instead, now embedder handles it.

---
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #23440 (GitHub issue number if applicable)

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- [ ] There are tests for these changes OR
- [X] These changes do not require tests because it is enough to test manually in input box, if copying and pasting still works .

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ports/libmlservo/src/lib.rs

@@ -378,6 +378,12 @@ impl HostTrait for HostCallbacks {
             keyboard(self.app, show)
         }
     }
+
+    fn get_clipboard_contents(&self) -> Option<String> {
+        None
+    }
+
+    fn set_clipboard_contents(&self, _contents: String) {}
 }
 
 pub struct ServoInstance {