chore: avoid alloc or fmt when possible

[tisonkun]

TRIVIAL AS IS.

[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.5%. Comparing base (285dc92) to head (03005bf).

Files with missing lines	Patch %	Lines
opentelemetry/src/common.rs	50.0%	2 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3183   +/-   ##
=====================================
  Coverage   80.5%   80.5%           
=====================================
  Files        126     126           
  Lines      22238   22238           
=====================================
  Hits       17921   17921           
  Misses      4317    4317           

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