Add Comprehensive Test Suite for Sourcify API Service

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This PR introduces a comprehensive test suite for the sourcify api service. The suite ensures the correctness and reliability of the various functions provided by the service. Here are the key changes:

• Adds a SourcifySuite struct that groups together all test cases.
• Includes test cases for functions such as GetContractMetadata, GetContractSourceCode, GetChains, GetAvailableContractAddresses, CheckContractByAddresses, GetHealth, and GetContractFiles.
• Each test function makes assertions to verify the correctness of the function under test. This includes checking that no error is returned, and validating returned values where applicable.
• Includes interoperability fixes for tree, source and address check functions.

These additions will ensure the robustness of the sourcify service by validating its responses against expected results. They will also help to identify any regressions that may occur during future development.

This PR closes #6.