Fix the size of return value by eth_getStorageAt

[Kourin1996]

Description

This PR makes eth_getStorageAt return 32 bytes data for any set storage.
For example, eth_getStorageAt in current Edge returns 4 bytes data for the storage where 2 uint16 values are stored. But other EVM chain always returns 32 bytes (at least as far as I checked in Goerli Ethereum Test Net and Mumbai Polygon PoS Test Net)

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

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Documentation update

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Additional comments

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[zivkovicmilos]

Looks good, thank you for the fix 🙏

[codecov]

Codecov Report

Merging #744 (6e22ed2) into develop (7ada10f) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #744      +/-   ##
===========================================
- Coverage    52.48%   52.48%   -0.01%     
===========================================
  Files          130      130              
  Lines        17069    17068       -1     
===========================================
- Hits          8959     8958       -1     
  Misses        7466     7466              
  Partials       644      644              

Impacted Files	Coverage Δ
jsonrpc/eth_endpoint.go	71.45% <100.00%> (-0.05%)	⬇️

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[zivkovicmilos]

@Kourin1996

You are clear to merge this 🚀