Issue str 100/macro buf impl

[sudikshyapant]

Description

This PR refactors the Buf20, Buf32, and Buf64 types to use a macro for generating their common implementations.

Type of Change

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature/Enhancement (non-breaking change which adds functionality or enhances an existing one)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation update
• [ ] Refactor
• [ ] New or updated tests

Checklist

• [x] I have performed a self-review of my code.
• [ ] I have commented my code where necessary.
• [ ] I have updated the documentation if needed.
• [ ] My changes do not introduce new warnings.
• [x] I have added tests that prove my changes are effective or that my feature works.
• [x] New and existing tests pass with my changes.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.23529% with 6 lines in your changes missing coverage. Please review.

Project coverage is 57.64%. Comparing base (a2d835c) to head (80e5529). Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/primitives/src/macros.rs	88.23%	6 Missing :warning:

@@            Coverage Diff             @@
##             main     #429      +/-   ##
==========================================
- Coverage   57.74%   57.64%   -0.11%     
==========================================
  Files         263      264       +1     
  Lines       27538    27685     +147     
==========================================
+ Hits        15902    15959      +57     
- Misses      11636    11726      +90     

Files with missing lines	Coverage Δ
crates/primitives/src/macros.rs	88.23% <88.23%> (ø)

... and 10 files with indirect coverage changes