Expand get_class testing

[FabijanC]

Usage related changes

None

Development related changes

• Add tests which declare a class, fetch it using starknet_getClass and assert equality with the original artifact
  • one for Cairo 0 and one for Cairo 1
  • the Cairo 0 test was failing (Circle CI failure link)
    • Close Cairo 0 artifact assertion is failing #434
• Add utility function for comparing Cairo 1 classes

Checklist:

• Applied formatting - ./scripts/format.sh
• No linter errors - ./scripts/clippy_check.sh
• No unused dependencies - ./scripts/check_unused_deps.sh
• Performed code self-review
• Rebased to the last commit of the target branch (or merged it into my branch)
• Documented the changes
• Linked the issues which this PR resolves
• Checked the TODO section in README.md if this PR resolves it
• Updated the tests
• All tests are passing - cargo test