Add error info for getKeyringForAccount

[andrepimenta]

The mobile team has seen multiple errors coming from "No keyring found for the requested account." so this PR adds more info to that error in order to help diagnosing the problem.
Sentry error: https://sentry.io/organizations/metamask/issues/2044540268/?project=2299799&referrer=github_integration
Mobile issue: MetaMask/metamask-mobile#2497

Resolves #86

[Gudahtt]

The text "No winners" and "No candidates" might end up being more confusing than helpful 🤔 Those terms don't have any meaning to consumers of this library. Maybe it would be more helpful to express these failure cases as three separate errors?

I see three separate scenarios:

• The address passed in is invalid/empty
• There are no keyrings
• There are keyrings, but none match the address.

[andrepimenta]

The text "No winners" and "No candidates" might end up being more confusing than helpful 🤔 Those terms don't have any meaning to consumers of this library. Maybe it would be more helpful to express these failure cases as three separate errors?

I see three separate scenarios:

• The address passed in is invalid/empty
• There are no keyrings
• There are keyrings, but none match the address.

I agree 100%! Just fixed, thank you!

[Gudahtt]

LGTM!

[cppfuns]

Encountered related problems, please take a look at this submission can solve the problem I encountered
MetaMask/metamask-mobile#2497 (comment)