Add ASV benchmark for trajectory iteration performance

[Anirudhpatil367]

Fixes #

Changes made in this Pull Request:

• Added an ASV benchmark to measure performance of trajectory iteration in MDAnalysis.
• The benchmark measures the time required to iterate through all frames of a trajectory using Universe.trajectory.
• Implemented a new benchmark file: benchmarks/benchmarks/trajectory_iteration.py.
• This helps monitor performance regressions or improvements in trajectory iteration across future commits.

LLM / AI generated code disclosure

LLMs or other AI-powered tools (beyond simple IDE use cases) were used in this contribution: yes

PR Checklist

• Issue raised/referenced?
• Tests updated/added?
• Documentation updated/added?
• package/CHANGELOG file updated?
• Is your name in package/AUTHORS? (If it is not, add it!)
• LLM/AI disclosure was updated.

Developers Certificate of Origin

I certify that I can submit this code contribution as described in the Developer Certificate of Origin, under the MDAnalysis LICENSE.

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📚 Documentation preview 📚: https://mdanalysis--5314.org.readthedocs.build/en/5314/

[Anirudhpatil367]

Hi! I am preparing my application for Google Summer of Code and started contributing by adding this benchmark for trajectory iteration.
Any feedback or suggestions for improvement would be greatly appreciated.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.82%. Comparing base (50dc512) to head (eba962c).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #5314   +/-   ##
========================================
  Coverage    93.82%   93.82%           
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  Files          182      182           
  Lines        22487    22487           
  Branches      3196     3196           
========================================
  Hits         21099    21099           
  Misses         925      925           
  Partials       463      463           

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