Rethink service and metadata files

[chasefleming]

Wallets who add themselves to Discovery may also eventually be discoverable through different plugins. We currently filter out duplicates since we needed a way to handle an extension being sent from FCL and an extension having added themselves to show as uninstalled. Service and metadata fields are also starting to become bloated since install links are required for different platforms. It's time to rethink how this is structured.