[skip actions] resolve with an error if merchantDisplayName isn't provided

[charliecruzan-stripe]

Summary

stripe-android will crash if you pass an empty string to the PaymentSheet.Configuration and then attempt to present the payment sheet, so let's catch that and resolve during the initialization step with an error.

Motivation

closes #980

Testing

• I tested this manually
• I added automated tests

Documentation

Select one:

• I have added relevant documentation for my changes.
• This PR does not result in any developer-facing changes.