Delete obsolete exception serialization benchmarks

[jack-berg]

These benchmarks were introduced in 2020 / 2021 around the time when Span.recordException was introduced. Since then, we've introduced a dedicated ExceptionAttributeResolver plugin interface, and have updated the default implementation to be attribute limits aware.

StacktraceRenderBenchmark performs the function of these benchmarks, testing the perf of the difference renders we provide, different shapes of exceptions, and different length limits.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.16%. Comparing base (87b0d9a) to head (7c34d16).
⚠️ Report is 6 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8029   +/-   ##
=========================================
  Coverage     90.16%   90.16%           
  Complexity     7484     7484           
=========================================
  Files           836      836           
  Lines         22562    22562           
  Branches       2237     2237           
=========================================
  Hits          20344    20344           
  Misses         1515     1515           
  Partials        703      703           

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