Fix span status report

[mariomac]

Span status report was reported as a numeric 0, 1, 2, where it should be a string: STATUS_CODE_OK, STATUS_CODE_ERROR or STATUS_CODE_UNSET.

Also, reported status code was always unset or error, but never OK.

Fixes #1773

[codecov]

Codecov Report

Attention: Patch coverage is 90.24390% with 4 lines in your changes missing coverage. Please review.

Project coverage is 67.26%. Comparing base (2a10f4a) to head (7c43f33).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/internal/request/span.go	92.30%	2 Missing ⚠️
pkg/export/prom/prom.go	50.00%	0 Missing and 1 partial ⚠️
pkg/internal/request/span_getters.go	66.66%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1784      +/-   ##
==========================================
+ Coverage   65.36%   67.26%   +1.90%     
==========================================
  Files         203      219      +16     
  Lines       20884    22607    +1723     
==========================================
+ Hits        13650    15207    +1557     
- Misses       6360     6631     +271     
+ Partials      874      769     -105     

Flag	Coverage Δ
integration-test	55.09% <80.48%> (+0.09%)	⬆️
k8s-integration-test	53.00% <48.78%> (-0.01%)	⬇️
oats-test	34.33% <43.90%> (+0.03%)	⬆️
unittests	43.48% <65.85%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[grcevski]

LGTM! Nice!

[bjor-joh]

Also, reported status code was always unset or error, but never OK.

So what I reported in #1773 was actually the opposite. Status was always ok but errors etc was not reported correctly.
But maybe the root cause is the same?