feat: Render declined calls in DM timeline (#5512)

* feat: Render declined calls in DM timeline

* Record preview snapshots

* review: Use CallIntent constant

* review: clean-up

* Record preview snapshots

* review: Move private field to the bottom with MARK: - Private

* review: Male CallIntent a string enum to use rawValue

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Co-authored-by: Element CI <ci@element.io>

UnitTests/Sources/ElementCallServiceTests.swift

@@ -148,6 +148,13 @@ final class ElementCallServiceTests {
             await testClock.advance(by: .seconds(100))
         }
     }
+    
+    @Test
+    func callIntentRawValues() {
+        // Test to ensure that the implicit rawValue of the string enum matches the MSC values
+        #expect(CallIntent.audio.rawValue == "audio")
+        #expect(CallIntent.video.rawValue == "video")
+    }
 }
 
 private class PKPushPayloadMock: PKPushPayload {