Return FullBlock from syncer

[goran-ethernal]

Description

This PR modifies the OnBlockInserted callback to consensus engine from syncer so that it returns a types.FullBlock (which contains transaction receipts as well, not just the block).

This is needed so that the consensus engine has all the necessary data for bridge to properly function, specifically exit workflow, since currently we are only extracting exit events when a block is inserted through consensus.

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)

Breaking changes

Please complete this section if any breaking changes have been made, otherwise delete it

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

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Codecov Report

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[ferranbt]

Overall looks good, only major thing is to remove the functionality from WriteFullBlock of executing the Block itself and move that to a custom function (this is, split what WriteBlock does in two steps).

[vcastellm]

Late LGTM