Tweaks to ActivityCreation benchmarks

[cijothomas]

1. Removed parentid, kind scenarios as they don't seem to add additional value over other benchmarks.

.2 Added a benchmark to compare the perf difference between using SetTag vs AddTag. The former does de-duplication+override, the latter does not do this. In scenarios where the tags are controlled (eg: Instrumentation Libraries from this repo), it might be faster to use AddTag instead of SetTag. This PR is simply adding benchmarks to help support that decision (in a future PR) for the instrumentations, and also give a recommendation to end users about the AddTag vs SetTag behavior.
Yes, SetTag is the spec-compliant API, but users who are in full control of their Tags might leverage AddTag to save some unwanted cpu cycles to detect duplicates. The cost increases with each attribute, as the current implementation traverses the list to look for duplicate.

[codecov]

Codecov Report

Merging #5173 (3a67f93) into main (3ffbef3) will decrease coverage by 0.19%.
Report is 1 commits behind head on main.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5173      +/-   ##
==========================================
- Coverage   83.43%   83.25%   -0.19%     
==========================================
  Files         297      297              
  Lines       12366    12366              
==========================================
- Hits        10318    10295      -23     
- Misses       2048     2071      +23     

Flag	Coverage Δ
unittests	83.25% <ø> (-0.19%)	⬇️

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see 8 files with indirect coverage changes