Update mock credentials

[alexfigtree]

Is your feature request related to a problem? Please describe.
Difficult to get mock creds to work when they're broken

Describe the solution you'd like

1. More mock creds of different types, perhaps some documentation incorporating Example Credential with CBOR-LD QR Code digitalcredentials/docs#10
2. Also include QR codes for each credential for wallet testing
3. Remove mock credentials hardcoded in wallet

Describe alternatives you've considered
N/A

Additional context
N/A

[alexfigtree]

From #466: https://docs.google.com/document/d/16zvVaRNGR9-0pbOq9P9WK6snY6KDEh2_vruX6FLM1uM/edit

[alexfigtree]

Related to #643