Log packages already in the global packages folder that are used in a restore

[zivkan]

We've had requests from multiple people that when a restore uses a package that already exists in the global packages folder, or a fallback folder, that we should log it.

I'm proposing that it's only output at diagnostic verbosity, so it doesn't spam most people.

Since HTTP and extracting/installed messages are listed once per restore, not once per project that uses the package, the new log messages for "existing package used" should also be only once per restore.