Ensure thrown errors always bubble to the extension appropriately

I haven't been able to determine if this problem is on the extension or keyring side, but it seems as though every error that occurs with Ledger integration makes its way to the extension UI as `Internal JSON-RPC error.`, which is incredibly unhelpful for the dev teams and users being able to report issues.

This should be a top priority moving forward with Ledger work.

Trace errors through the Ledger integration and keyring boundary to the extension UI, first determining whether the loss of detail occurs in the extension or on the keyring side. Done means errors reach users and development teams with useful underlying details instead of only “Internal JSON-RPC error.”

Written by the indexing model from the issue text.