Support v2 address credentials (CAP-71) #1562

RPC simulation will start returning v2 address credentials on an upcoming protocol boundary (CAP-71). The JS SDK needs to support v2 credentials alongside the existing v1 support.

We should keep v1 working and add v2 support in parallel.

• Parse v2 address credentials returned from simulation.
• Sign v2 address credentials (authorizeEntry / authorizeInvocation and equivalents).
• Add a way to opt in to requesting v2 credentials from RPC simulateTransaction (not yet implemented).

Slack discussion context (https://stellarfoundation.slack.com/archives/C030Z9EHVQE/p1784664824151599)