chore(all): return concrete types, accept interfaces

- Remove exported interfaces unused locally
- Define interfaces to accept arguments
- Return concrete types, not interfaces

internal/provider/common/mocks_generate_test.go

@@ -2,4 +2,4 @@ package common
 
 // Exceptionally, these mocks are exported since they are used by all
 // provider subpackages tests, and it reduces test code duplication a lot.
-//go:generate mockgen -destination=mocks.go -package $GOPACKAGE . ParallelResolver,Storage
+//go:generate mockgen -destination=mocks.go -package $GOPACKAGE . ParallelResolver,Storage,Unzipper