[Spark Load] [Bug] Load job's state will stay in ETL state all the time after FE restart

[xy720]

Proposed changes

fix #4519

How to reproduce:
Restart when the state is ETL

1. Submit a spark load job
2. Wait until the job state become ETL
3. Restart FE
4. Show load. And you can see the state of the job will always be stuck in ETL with progress 0%.
5. Open the web interface of the yarn cluster with browser, you can see that the spark job has been submitted successfully and is running well and normally.

Expected behavior
The job state should be ETL after FE restart. And the state will not stuck in ETL.

The Reson of this BUG
This is because SparkLoadAppHandle in SparkLoadJob is not persisted, resulting in that an NPE error thrown in the ETL phase after FE restart, making the job state stay in the ETL state all the time.

Types of changes

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• Bugfix (non-breaking change which fixes an issue)

Checklist

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• I have create an issue on (Fix [Spark Load][Bug] Load job's state is incorrect after FE restart #4519), and have described the bug/feature there in detail

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[morningman]

LGTM