Remove use of ProviderBuilder by repo handler

[dmjb]

Relates to #2845

1. Move the bulk provider instantiation for remote repo listing behind the provider manager interface.
2. Change the repo creation method in the repo service to instantiate its own provider. The handler still queries the table of providers to search for an appropriate provider. I have decided to not put this behind the ProviderManager at this time since I feel like the right place to do this sort of logic may change in subsequent PRs.

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[coveralls]

coverage: 50.359% (-0.3%) from 50.625%
when pulling 954e589 on cleanup-repo-endpoints-providers
into b9daa61 on main.