improve package supplier fallback logic ...

- scope (failure) did swallow fatal errors
- improve logging of failures and successes
- rethrow failure of default registry instead of from the last one
- remove failing package suppliers, so we don't keep beating dead horses

Note that some retry logic is already done interally by package suppliers,
so a failing one is unlikely to recover on the next usage.

Filesystem package supplier updated

Retry download for registry search packages

Refactor retry download

Split-up package suppliers into individual modules