RegistryCredentialsOptions was mistakenly removed from GetStaleImagesCommand

[lbussell]

...in #1293.

We need the RegistryCredentialsOptions on GetStaleImagesCommand so that we can pass in our DockerHub credentials to avoid rate-limiting. The option was mistakenly removed in the above linked PR.

#1298 can be reverted after this is fixed.

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.