refactor: introduce cursor for serialization

[MrCroxx]

What's changed and what's your intention?

Please explain IN DETAIL what the changes are in this PR and why they are needed. :D

This PR introduces trait Cursor for serialization to reduce buffer copy.

It will be used in further PRs.

Checklist

• I have written necessary rustdoc comments
• I have added necessary unit tests and integration tests
• I have passed make check and make test or make all in my local envirorment.

Related issues or PRs (optional)

#216 #226

[codecov]

Codecov Report

Attention: 74 lines in your changes are missing coverage. Please review.

Comparison is base (fb5cd5e) 77.37% compared to head (4b2762a) 76.38%.

Files	Patch %	Lines
foyer-common/src/code.rs	0.00%	74 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #227      +/-   ##
==========================================
- Coverage   77.37%   76.38%   -1.00%     
==========================================
  Files          47       47              
  Lines        5685     5759      +74     
==========================================
  Hits         4399     4399              
- Misses       1286     1360      +74     

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[Li0k]

LGTM