[SPARK-48660][SQL] Fix explain result for CreateTableAsSelect

[yuexing]

What changes were proposed in this pull request?

To fix the explain result of 'CreateTableAsSelect', according to how ExplainCommand processes, I find out the following work is needed

• CreateDataSourceTableAsSelectCommand should implement stats
• ExecutedCommandExec should also implement innerChildren for CreateDataSourceTableAsSelectCommand

Here's why:

• As to 'CREATE TABLE ... AS SELECT'
• CreateDataSourceTableAsSelectCommand will finally be the LogicPlan
• ExecutedCommandExec(cmd=CreateDataSourceTableAsSelectCommand) will finally be the PhysicalPlan

Thus , to have the expected output

• CreateDataSourceTableAsSelectCommand adds stats implementation
• ExecutedCommandExec adds innerChildren for QueryExecution.stringWithStats

Why are the changes needed?

as reported in SPARK-48660, explain result of 'CreateTableAsSelect' is incorrect. It's missing stats for logic plan and optimization for physical plan.

Does this PR introduce any user-facing change?

Yes, it affects the explain result.

How was this patch tested?

UT.

Was this patch authored or co-authored using generative AI tooling?

No

[LuciferYang]

cc @wangyum FYI

[LuciferYang]

Could you fix the failed tests first? @yuexing

[LuciferYang]

The result seems correct. Do you have time to review this one? @wangyum

[LuciferYang]

friendly ping @wangyum

[github-actions[bot]]

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