Provide module for Vec<u8> to hex string serialization

[vkgnosis]

We use web3::Bytes in a couple of places solely because it serializes to 0x prefixed hex string which we want in some apis. This behavior is not documented so we shouldn't rely on it. This PR introduces a custom serialization module with the same functionality.

Test Plan

CI, unit tests

[codecov-commenter]

Codecov Report

Merging #186 (b26bae8) into main (d0eed4b) will increase coverage by 0.00%.
The diff coverage is 83.33%.

❗ Current head b26bae8 differs from pull request most recent head d9ff6d6. Consider uploading reports for the commit d9ff6d6 to get more accurate results

@@           Coverage Diff           @@
##             main     #186   +/-   ##
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  Coverage   64.58%   64.59%           
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  Files         185      186    +1     
  Lines       38602    38629   +27     
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+ Hits        24932    24952   +20     
- Misses      13670    13677    +7