[UT] test isolation workgroup manager

[eshishki]

Summary

Fix test isolation issues introduced in #66690 and #63956.

When tests run in the same process (without gtest-parallel),
ResourceGroupUsageRecorderTest replaces workgroup_manager without calling
start(), leaving driver_executor as nullptr. This causes subsequent tests
to crash with nullptr dereference.

Changes

• ResourceGroupUsageRecorderTest: save/restore original workgroup_manager, call start()
• PipeLineFileScanNodeTest: add missing set_workgroup() call

What type of PR is this:

• BugFix
• Feature
• Enhancement
• Refactor
• UT
• Doc
• Tool

Does this PR entail a change in behavior?

• Yes, this PR will result in a change in behavior.
• No, this PR will not result in a change in behavior.

If yes, please specify the type of change:

• Interface/UI changes: syntax, type conversion, expression evaluation, display information
• Parameter changes: default values, similar parameters but with different default values
• Policy changes: use new policy to replace old one, functionality automatically enabled
• Feature removed
• Miscellaneous: upgrade & downgrade compatibility, etc.

Checklist:

• I have added test cases for my bug fix or my new feature
• This pr needs user documentation (for new or modified features or behaviors)
  • I have added documentation for my new feature or new function
  • This pr needs auto generate documentation
• This is a backport pr

Bugfix cherry-pick branch check:

• I have checked the version labels which the pr will be auto-backported to the target branch
  • 4.1
  • 4.0
  • 3.5
  • 3.4
  • 3.3

---

Note

Ensures test isolation and proper workgroup setup to avoid nullptr crashes across tests.

• ResourceGroupUsageRecorderTest: replace exec_env._workgroup_manager with a started instance, then restore the original at the end
• PipeLineFileScanNodeTest: call _fragment_ctx->set_workgroup(ExecEnv::GetInstance()->workgroup_manager()->get_default_workgroup()) in SetUp()

^{Written by Cursor Bugbot for commit 0545875. This will update automatically on new commits. Configure here.}

[alvin-phoenix-ai]

@cursor review

[cursor]

✅ Bugbot reviewed your changes and found no bugs!

[github-actions]

[Java-Extensions Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[FE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[github-actions]

[BE Incremental Coverage Report]

✅ pass : 0 / 0 (0%)

[eshishki]

@alvin-celerdata could you take a look when you have a moment? This is a small BE UT-only fix for test isolation in the workgroup manager.

[github-actions]

@Mergifyio backport branch-4.1

[mergify]

backport branch-4.1

✅ Backports have been created

Details

• #73322 [UT] test isolation workgroup manager (backport #67489) has been created for branch branch-4.1 but encountered conflicts

Cherry-pick of a58a55f has failed:

On branch mergify/bp/branch-4.1/pr-67489
Your branch is up to date with 'origin/branch-4.1'.

You are currently cherry-picking commit a58a55faf7.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   be/test/agent/resource_group_usage_recorder_test.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   be/test/exec/pipeline/pipeline_file_scan_node_test.cpp

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally