[SPARK] Avoid trigger execution when getting result schema

[wForget]

:mag: Description

Issue References 🔗

DataFrame.isEmpty may trigger execution again, we should avoid it.

Describe Your Solution 🔧

Types of changes :bookmark:

• [X] Bugfix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Test Plan 🧪

Behavior Without This Pull Request :coffin:

Behavior With This Pull Request :tada:

Related Unit Tests

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Checklist 📝

• [X] This patch was not authored or co-authored using Generative Tooling

Be nice. Be informative.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 10 lines in your changes missing coverage. Please review.

Project coverage is 0.00%. Comparing base (7198c72) to head (265f0ec). Report is 19 commits behind head on master.

Files with missing lines	Patch %	Lines
...kyuubi/engine/spark/operation/SparkOperation.scala	0.00%	5 Missing :warning:
.../kyuubi/engine/spark/operation/ExecutePython.scala	0.00%	2 Missing :warning:
...e/kyuubi/engine/spark/operation/ExecuteScala.scala	0.00%	2 Missing :warning:
...ubi/engine/spark/operation/PlanOnlyStatement.scala	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #6688 +/- ## ====================================== Coverage 0.00% 0.00% ====================================== Files 684 684 Lines 42237 42277 +40 Branches 5755 5765 +10 ====================================== - Misses 42237 42277 +40 ```

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[pan3793]

cc @iodone

[bowenliang123]

Thanks, merged to master (1.10.0) and branch-1.9 (1.9.3).