feat(Improvements): Migrate downloader package from legacy jacobsa dependency to testify.

[charith87]

Description

Migrate tests in internal/cache/file/downloader from legacy ogletest to testify:

• downloader_test.go: Convert to standard Test_* functions with newDownloaderTest(t) helper, t.TempDir(), and assert/require.
• job_test.go: Convert suite methods to standalone tests using newJobTest(t) and testify assertions.
• parallel_downloads_job_test.go: Migrate parallel download test suite to testify.
• sparse_downloads_job_test.go: Migrate sparse download tests to table-driven tests with testify.

Link to the issue in case of a bug fix.

N/A

Testing details

1. Manual - make build passed.
2. Unit tests - go test -v -count=1 ./internal/cache/file/downloader/... passed.
3. Integration tests - N/A

Any backward incompatible change? If so, please explain.

N/A

[gemini-code-assist]

Code Review

This pull request refactors the downloader tests by migrating from the ogletest framework to the standard Go testing package combined with testify/assert and testify/require. The review feedback highlights several critical issues with the migration: first, using require assertions (which invoke FailNow()) inside background goroutines is unsafe and can cause silent failures or hangs, meaning assert should be used instead. Second, assertions within subtests (t.Run) must use the subtest's local t context rather than the parent's context to ensure proper test isolation and accurate failure reporting.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.88%. Comparing base (872920d) to head (7a2b58c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5029      +/-   ##
==========================================
- Coverage   83.90%   83.88%   -0.02%     
==========================================
  Files         176      176              
  Lines       21546    21546              
==========================================
- Hits        18078    18074       -4     
- Misses       2769     2772       +3     
- Partials      699      700       +1     

Flag	Coverage Δ
unittests	83.88% <ø> (-0.02%)	⬇️

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