Allow a credential provider to opt into always using default type icons when it's the only provider

Decision of entry icon display logic
- One account available
   - Provider icon on top
   - Generic icon for front page entry when opt in
   - Provider sent icon on secondary page unconditionally
- Multiple accounts coming from a single provider
   - Provider icon on top
   - Generic icon for front page entry when opt in
   - Provider sent icon on secondary page unconditionally

Bug: 319723933
Test: see screenshots attached to bug
Change-Id: I36aa6f583c001af2a3be3fad80739ce56ddaf06e