Add obsolete ResponseMimeType alias for ResponseContentType

A new property `ResponseContentType` has been added to the `ApiCallDetails` class. This reintroduces the original `ResponseMimeType` property marked as obsolete and serves as a temporary alias for the existing `ResponseContentType` property.

src/Elastic.Transport/Responses/HttpDetails/ApiCallDetails.cs

@@ -82,6 +82,17 @@ public string DebugInformation
 	/// </summary>
 	public byte[]? ResponseBodyInBytes { get; internal set; }
 
+	/// <summary>
+	/// The value of the Content-Type header in the response.
+	/// </summary>
+	[Obsolete("This property has been retired and replaced by ResponseContentType. " +
+		"Prefer using the updated property as this will be removed in a future release.")]
+	public string ResponseMimeType
+	{
+		get => ResponseContentType;
+		set => ResponseContentType = value;
+	}
+
 	/// <summary>
 	/// The value of the Content-Type header in the response.
 	/// </summary>