fix: Custom attribute values of type float and decimal were not serialized correctly.

[tippmar-nr]

Custom attribute values of type float or decimal could, in some cases, be serialized with a different precision than the original value (i.e., 0.2f would be serialized as 0.20000000298023224) due to a conversion to double prior to serialization.

Adds unit tests to verify correct behavior.

fixes #2945

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.15%. Comparing base (b141eee) to head (fa079bd).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2975      +/-   ##
==========================================
- Coverage   82.16%   82.15%   -0.01%     
==========================================
  Files         473      473              
  Lines       30334    30335       +1     
  Branches     3387     3387              
==========================================
- Hits        24923    24921       -2     
- Misses       4612     4617       +5     
+ Partials      799      797       -2     

Flag	Coverage Δ
Agent	83.13% <100.00%> (-0.02%)	⬇️
Profiler	73.13% <ø> (ø)

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Files with missing lines	Coverage Δ
...Relic/Agent/Core/Attributes/AttributeDefinition.cs	84.22% <100.00%> (+0.05%)	⬆️

... and 4 files with indirect coverage changes