chore: prepare opentelemetry_sdk 0.32.1 release

[lalitb]

Changes

• Bump opentelemetry_sdk from 0.32.0 to 0.32.1.
• Move current SDK changelog entries under a new 0.32.1 release section.

Notes

This is a patch release for opentelemetry_sdk only. The crate continues to depend on opentelemetry = ^0.32, so no opentelemetry crate release is needed.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.9%. Comparing base (a389ca6) to head (adc9005).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #3522   +/-   ##
=====================================
  Coverage   82.9%   82.9%           
=====================================
  Files        130     130           
  Lines      27311   27311           
=====================================
  Hits       22649   22649           
  Misses      4662    4662           

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[lalitb]

@open-telemetry/rust-approvers - please approve this - need this for security/advisory fix.