Shell executor logs through testing.T in upgrade tests

[mgencur]

Similar to knative/serving#14495

Fixes #

Proposed Changes

• Print logs from shell executor to testing.T so that the logs can be found within test scope

Pre-review Checklist

• At least 80% unit test coverage
• E2E tests for any new behavior
• Docs PR for any user-facing impact
• Spec PR for any new API feature
• Conformance test for any change to the spec

Release Note

Docs

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (f9314d8) 76.87% compared to head (a0505b4) 76.84%.
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7367      +/-   ##
==========================================
- Coverage   76.87%   76.84%   -0.03%     
==========================================
  Files         252      252              
  Lines       13822    13822              
==========================================
- Hits        10625    10622       -3     
- Misses       2667     2669       +2     
- Partials      530      531       +1     

see 1 file with indirect coverage changes

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[mgencur]

Printing within test scope can be seen in this run
Now removing the temporary commit to make the tests pass.

[mgencur]

/test reconciler-tests

[creydr]

/lgtm

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: creydr, mgencur

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[knative-prow]

@mgencur: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
upgrade-tests_eventing_main	a0505b4	link	unknown	/test upgrade-tests

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