Feat: Add OTel Tracing Headers and Baggage with CueX Requests

[briankane]

Description of your changes

Adds tracing and baggage (app context) support using OTel for outbound CueX requests.
The externalserver package has been updated to reconstruct the context from the received headers.

I have:

• Read and followed KubeVela's contribution process.
• Related Docs updated properly. In a new feature or configuration option, an update to the documentation is necessary.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

How has this code been tested

PR includes unit tests for both the outbound and inbound functionality.
Manual testing has been conducted to ship application workflow context & trace IDs from a Kubevela Application to a CueX server.

Special notes for your reviewer

N/A

[codecov]

Codecov Report

Attention: Patch coverage is 92.85714% with 8 lines in your changes missing coverage. Please review.

Project coverage is 86.71%. Comparing base (5199730) to head (1844bda).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
cue/cuex/runtime/tracer.go	92.52%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #115      +/-   ##
==========================================
+ Coverage   86.46%   86.71%   +0.24%     
==========================================
  Files          81       82       +1     
  Lines        3959     4071     +112     
==========================================
+ Hits         3423     3530     +107     
- Misses        402      408       +6     
+ Partials      134      133       -1     

Flag	Coverage Δ
unit-test	86.71% <92.85%> (+0.24%)	⬆️

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[FogDong]

Thanks for adding it!