refactor: Do not call teardown manually in tests

[alexandear]

The PR refactors the setup function by passing *testing.T parameter and calling t.Cleanup(server.Close) inside. So a test that using setup doesn't need to call manually teardown.

This leads to removal of 1319 code lines in tests.

[gmlewis]

Thank you, @alexandear !
One important change, please, then we should be ready for a second LGTM+Approval from any other contributor to this repo before merging.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.97%. Comparing base (2b8c7fa) to head (2ea32d3).
Report is 129 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3293 +/- ##
==========================================
- Coverage 97.72% 92.97% -4.75% 
==========================================
Files 153 171 +18 Lines 13390 11715 -1675 ==========================================
- Hits 13085 10892 -2193 - Misses 215 729 +514 - Partials 90 94 +4 

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[gmlewis]

Thank you, @alexandear !
LGTM.

Awaiting second LGTM+Approval from any other contributor to this repo before merging.

[tomfeigin]

LGTM

[gmlewis]

Thank you, @tomfeigin !
Merging.