fix: Should fix failures reading subnet contract version

[jbencin]

Description

Properly deserialize response from call to read-only function get-version in subnet.clar

Applicable issues

• fixes Subnet contract version check doesn't work right #276

Additional info (benefits, drawbacks, caveats)

This is somewhat messy, and contains some unwrap()s and panic!()s when things don't go as expected (although I don't really expect them to ever be triggered). We are trying to get this out ASAP, so I'll clean up later.

Checklist

• Test coverage for new or modified code paths
• Changelog is updated
• Required documentation changes (e.g., docs/rpc/openapi.yaml and rpc-endpoints.md for v2 endpoints, event-dispatcher.md for new events)
• New clarity functions have corresponding PR in clarity-benchmarking repo
• New integration test(s) added to bitcoin-tests.yml

[obycode]

LGTM!