Fix DownloadState.get_ratio()

[drew2a]

This PR fixes #7817 by changing the function to the following:

    def get_all_time_ratio(self) -> float:
        if not self.lt_status or not self.all_time_download:
            return 0
        return self.all_time_upload / self.all_time_download

[kozlovsky]

I added the comment to the original issue #7817. It looks like the previous formula is correct (except when the total_done is zero), and instead of changing the formula, we should display the all_time_upload / all_time_download counters.

[drew2a]

@kozlovsky thank you. I've changed the function to the following:

    def get_all_time_ratio(self) -> float:
        if not self.lt_status or not self.all_time_download:
            return 0
        return self.all_time_upload / self.all_time_download

Also, I've changed the UI, please check the screenshot in the description for this issue.