Update QR code URI with API prefix

[sekimondre]

Description

Extend the WalletConnect URI implementation to include a prefix that specifies the target API.

• The prefix needs to be queryable so the app can conditionally route the pairing URI to the correct API.
• For Auth URI, the prefix is auth-.
• To account for backward compatibility, the absence of the prefix should be equivalent to a sign- prefix.

Example

"wc:auth-7f6e504bfad60b485450578e05678ed3e8e8c4751d3c6160be17160d63ec90f9@2?relay-protocol=irn&symKey=587d5484ce2a2a6ee3ba1962fdd7e8588e06200c46823bd18fbd67def96ad303"

[llbartekll]

irrelevant