fix: unwrap errors.Join() created joined errors in Context.Error()

[larkwins]

Automatically unwrap errors created by errors.Join() when passed to
Context.Error(), so they are added as separate error entries instead
of a single combined error. This improves error log readability and
structure.

Before:
Error #1: gin error
Error #2: service error
store error
Error #3: other error

After:
Error #1: gin error
Error #2: service error
Error #3: store error
Error #4: other error

Closes #4237

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.37%. Comparing base (3dc1cd6) to head (e262534).
⚠️ Report is 275 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4592      +/-   ##
==========================================
- Coverage   99.21%   98.37%   -0.84%     
==========================================
  Files          42       48       +6     
  Lines        3182     3146      -36     
==========================================
- Hits         3157     3095      -62     
- Misses         17       42      +25     
- Partials        8        9       +1     

Flag	Coverage Δ
	?
--ldflags="-checklinkname=0" -tags sonic	98.36% <100.00%> (?)
-tags go_json	98.30% <100.00%> (?)
-tags nomsgpack	98.35% <100.00%> (?)
go-1.18	?
go-1.19	?
go-1.20	?
go-1.21	?
go-1.25	98.37% <100.00%> (?)
go-1.26	98.37% <100.00%> (?)
macos-latest	98.37% <100.00%> (-0.84%)	⬇️
ubuntu-latest	98.37% <100.00%> (-0.84%)	⬇️

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