Single Domain UI Improvements

On accounts that have only a single domain, the UI should automatically select that domain on any page that allows for domain selection. For example, the following pages should automatically select the only domain in the account when visiting them: Domain Health Hosted Services -> Hosted SPF Hosted Services -> Hosted DMARC Hosted Services -> Hosted DKIM Hosted Services -> Hosted BIMI Hosted Services -> Hosted MTA-STS For all accounts that have more than 1 domain, I should need to select the domain on those pages.