Add option for download update file name.

[nhanchaukp]

In some cases, updates need to be downloaded from URLs that do not contain a properly formatted file name.
For example:
https://example.com/download/aW90L2lvdHNvZnR3YXJlLzIwMjUvMDIvMjYvMTc0MDU3NDg1MjQ3OC56aXA=

In this case, the Content-Disposition header in the response must be used to determine the file name. However, if it is missing, the downloaded file will be saved as aW90L2lvdHNvZnR3YXJlLzIwMjUvMDIvMjYvMTc0MDU3NDg1MjQ3OC56aXA=, which can cause issues. For example, it may not be possible to extract the file (if it lacks a .zip extension) or execute it (if it lacks a .exe extension), leading to an update failure.

In this update, users can manually specify the desired file name using UpdateInfoEventArgs.DownloadFileName.
For example:

UpdateInfoEventArgs.DownloadFileName = "Update.zip";