Remove additional fields returned compared to RPC spec

[marioiordanov]

Usage related changes

Every method without exceptions follows the format of the RPC spec

Development related changes

Removed contract_class property from Declare transactions.
Removed serialization/deserialziation of contract_address property in DeployAccount transactions.
Refactored handle_transaction_result to accept new argument of type ContractClass.
Edited spec_instructions to not generate data for DeclareV0 txns, because they are not supported.
Removed TODO statement in json_rpc::spec_reader::mod::test_spec_methods test

NEW
Removed EXPECTED_RPC_VERSION and used instead RPC_SPEC_VERSION

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