[chore] [cmd/mdatagen] Fix Windows CI test failures due to missing scraperhelper dependency

[jkoronaAtCisco]

Description

The TestLoader_LoadFromHTTP_Success/NotFound/ServerError tests in internal/schemagen were failing on all Windows CI runners with:

  failed to run `go get` for module go.opentelemetry.io/collector/scraper/scraperhelper: exit status 1                                                                                             

The root cause: loadFromHTTP calls refVersion, which uses packages.Load to resolve the module version of go.opentelemetry.io/collector/scraper/scraperhelper. Because scraperhelper was not listed in internal/schemagen/go.mod, packages.Load returned nothing on fresh Windows CI environments where the module was not in the cache. The code then fell back to go get, which failed (network restrictions / inability to modify the module on CI).

The fix adds scraperhelper as an explicit dependency of internal/schemagen and adds a blank import in loader_test.go so go mod tidy retains the entry.

Link to tracking issue

Fixes #15285

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.24%. Comparing base (d3b2c86) to head (4882f55).
⚠️ Report is 43 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15286      +/-   ##
==========================================
- Coverage   91.25%   91.24%   -0.02%     
==========================================
  Files         705      705              
  Lines       46082    46082              
==========================================
- Hits        42054    42046       -8     
- Misses       2822     2828       +6     
- Partials     1206     1208       +2     

☔ 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.

[codspeed-hq]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 7 untouched benchmarks
⏩ 76 skipped benchmarks¹

---

_{Comparing jkoronaAtCisco:loader_test_fix (4882f55) with main (d3b2c86)}

Footnotes

1. 76 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[codeboten]

needs a rebase

[dmitryax]

mdatagenDir(t) returns filepath.Join(filepath.Dir(file), "../.."), which from internal/schemagen/ resolves to the repo root. So the go get is called from the root. If I understand that correctly, this fix won't help.

[dmitryax]

We should not add new go dependency with all these replaces to make tests happy. The tests should be updated instead.

[jkoronaAtCisco]

Good call, I updated the tests instead: replaced mdatagenDir(t) with a schemagenDir(t) helper that returns internal/schemagen/ itself, and switched the ref module from scraperhelper to confmap (a direct dep
with a local replace). packages.Load resolves the version immediately from there, so the go get fallback is never reached. No go.mod or go.sum changes needed.