feat(storage): add telemetry for pre-warmed ranges in ObjectDescriptorImpl

[kalragauri]

This PR adds OpenTelemetry instrumentation for multi-range pre-warming requests in the GCS async client.

[gemini-code-assist]

Code Review

This pull request introduces tracking and telemetry for the cache status ("HIT", "MISS", "EVICTED") of pre-warmed ranges in ObjectDescriptorImpl, recording it as an OpenTelemetry span attribute. The review feedback suggests limiting the size of the new evicted_ranges_ set to prevent unbounded memory growth, and optimizing performance by using absl::string_view instead of std::string to avoid unnecessary copies of the cache status.

[codecov]

Codecov Report

❌ Patch coverage is 73.91304% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.24%. Comparing base (849ed7b) to head (74d6e87).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...d/storage/internal/async/object_descriptor_impl.cc	63.63%	4 Missing ⚠️
...cloud/storage/internal/async/connection_tracing.cc	33.33%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16323   +/-   ##
=======================================
  Coverage   92.24%   92.24%           
=======================================
  Files        2227     2227           
  Lines      209234   209247   +13     
=======================================
+ Hits       192999   193013   +14     
+ Misses      16235    16234    -1     

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