Add Ethereum BLS Signature verification tests

[petscheit]

Adds a cairo program that can verify Ethereum beacon chain signatures. The ethereum test contains a valid block from the sepolia testnet.

Pull Request type

Please check the type of change your PR introduces:

• [ ] Bugfix
• [x] Feature
• [ ] Code style update (formatting, renaming)
• [ ] Refactoring (no functional changes, no API changes)
• [ ] Build-related changes
• [ ] Documentation content changes
• [x] Testing
• [ ] Other (please describe):

Does this introduce a breaking change?

• [ ] Yes
• [x] No

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