Uniform jsonrpc type return

[ferranbt]

Description

This PR use the return types in the jsonrpc package instead of an explicit conversion inside the endpoint.

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

Manual tests

Please complete this section if you ran manual tests for this functionality, otherwise delete it

Documentation update

Please link the documentation update PR in this section if it's present, otherwise delete it

Additional comments

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[Stefan-Ethernal]

Overall looks good to me, although unit tests are failing, because it is needed to change assertions (due to changes in return types string vs arg...
https://github.com/0xPolygon/polygon-edge/actions/runs/3401432822/jobs/5677755750

[ferranbt]

Overall looks good to me, although unit tests are failing, because it is needed to change assertions (due to changes in return types string vs arg...

Thank you! I did fail before due to the multi-lock error so I missed this error.

[vcastellm]

LGTM