tests(vision): normalize VPCSC configuration in systests (#9620)

* tests(vision): normalize VPCSC configuration in systests

- Use 'vpcsc_config' test utility for parsing VPCSC env vars, skipping.
- Use idiomatic 'with pytest.raises' for blocked methods.
- Avoid calling 'unique_id()' more than once.
- Remove test for VPCSC of storage client.

* fix: blacken

* fix: lint

* fix: update partial error message

Per request from @brendanlundy:
#9620 (comment)