Add tests for EIP 7549

[bshastry]

Issue Addressed

Expand Electra attestation test suite

Proposed Changes

This PR adds comprehensive test coverage for Electra attestations, focusing on equivalence with base attestations and multi-committee functionality. Added tests include:

1. Basic Creation Equivalence Test:

#[test]
fn test_creation_equivalence() {
    // Verifies that Electra attestations maintain equivalent basic properties
    // with Base attestations while supporting committee tracking
}

2. Signature Verification:

#[test]
fn test_signature_equivalence() {
    // Ensures signature creation and verification work identically 
    // between Base and Electra attestations
}

3. Aggregation Testing:

#[test]
fn test_aggregation_equivalence() {
    // Validates that aggregation behavior matches between
    // Base and Electra attestations
}

4. Error Handling:

#[test]
fn test_error_handling_equivalence() {
    // Confirms error conditions are handled consistently
    // across both attestation types
}

5. Multi-Committee Support:

#[test]
fn test_multi_committee_aggregation() {
    // Tests Electra's unique ability to handle multiple committees
    // in a single attestation
}

Additional Info

Test Coverage Focus

• Base vs Electra equivalence for backward compatibility
• Multi-committee functionality specific to Electra
• Edge cases in signature aggregation
• Error handling consistency

Testing Notes

1. Uses create_test_data() helper for consistent test scenarios
2. Explicitly tests both single and multi-committee cases
3. Verifies bit manipulation for committee tracking
4. Ensures proper index translation between committee spaces

Review Considerations

• Pay special attention to the multi-committee test cases
• Verify error handling matches existing behavior
• Check signature aggregation correctness
• Confirm committee bit manipulation is correct