Checkpoint submission e2e test

[Stefan-Ethernal]

Description

This PR implements basic use case for checkpoint submission, which checks whether epoch ending block was checkpointed succesfully.

It also fixes a bug in rootchain init-contracts command, since validators info wasn't resolved correctly (i.e. wrong directory was resolved).

Changes include

• Bugfix (non-breaking change that solves an issue)
• Hotfix (change that solves an urgent issue, and requires immediate attention)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the relevant labels
• I have updated the official documentation
• I have added sufficient documentation in code

Testing

• I have tested this code with the official test suite
• I have tested this code manually

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (feature/v3-parity@9e4ec91). Click here to learn what that means.
The diff coverage is n/a.

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  Misses                       ?     9058           
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