[PoC] Refactor attribute.Value implementation

[MrAlias]

Proof-of-concept for #4983

[codecov]

Codecov Report

Attention: Patch coverage is 84.97854% with 35 lines in your changes are missing coverage. Please review.

Project coverage is 82.8%. Comparing base (561714a) to head (90632c2).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #4985     +/-   ##
=======================================
- Coverage   82.9%   82.8%   -0.1%     
=======================================
  Files        238     240      +2     
  Lines      19127   19252    +125     
=======================================
+ Hits       15858   15945     +87     
- Misses      2980    3016     +36     
- Partials     289     291      +2     

Files	Coverage Δ
attribute/internal/fnv/fnv.go	100.0% <100.0%> (ø)
attribute/kv.go	92.3% <100.0%> (+0.6%)	⬆️
attribute/hash.go	77.7% <77.7%> (ø)
attribute/set.go	79.3% <73.6%> (-1.1%)	⬇️
attribute/value.go	86.3% <87.3%> (-4.9%)	⬇️

... and 9 files with indirect coverage changes