Blockscout v2 contract verification (#3576)
## Problem solved
Short description of the bug fixed or feature added
## Changes made
- [ ] Public API changes: list the public API changes made if any
- [ ] Internal API changes: explain the internal logic changes
## How to test
- [ ] Automated tests: link to unit test file
- [ ] Manual tests: step by step instructions on how to test
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## PR-Codex overview
This PR focuses on adding support for Blockscout v2 contract verification.
### Detailed summary
- Added `ExplorerType` enum for different explorer types
- Modified contract verifier to handle Blockscout v2 verification
- Updated verification functions to support different explorer types
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