fix: change value type of Baggage to StringValue

[gruebel]

Fixes #2716

Changes

• I had to make it a breaking change, I don't think it is possible to do it via deprecation

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

Attention: Patch coverage is 83.78378% with 6 lines in your changes missing coverage. Please review.

Project coverage is 79.4%. Comparing base (91ae096) to head (c0fe22c).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
opentelemetry/src/baggage.rs	64.7%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #2729     +/-   ##
=======================================
- Coverage   79.4%   79.4%   -0.1%     
=======================================
  Files        123     123             
  Lines      22737   22748     +11     
=======================================
+ Hits       18060   18063      +3     
- Misses      4677    4685      +8     

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[cijothomas]

@gruebel Thanks for addressing this!
@fraillt has made a few perf improvements and bug fixes to this, but unfortunately that was not merged
#2284

I agree it is not possible to do this without breaking, so let's do it. I also think we should make sure we can review Baggage entirely and finish up all breaking changes (if any) before next release, and mark Baggage also as RC status, preventing further breaking changes to it.

[gruebel]

Oh nice, didn't see that PR. I can wait till his changes are merged and then rebase my afterwards or vice versa.

[cijothomas]

LGTM.
Its breaking change, but necessary cost to take to get to stable.

[cijothomas]

Oh nice, didn't see that PR. I can wait till his changes are merged and then rebase my afterwards or vice versa.

Merged this one first as this is affecting public API and want to get Baggage towards stable/rc by next release.
@fraillt Could you resubmit the PR for perf improvements in Baggage?

Apologies for the delay - I was focused on Logs/Metrics and only now had bandwidth to look at Baggage!