[SPARK-38932][SQL] Datasource v2 support report distinct keys

[ulysses-you]

What changes were proposed in this pull request?

• Add a new mix in interface SupportsReportDistinctKeys for datasource v2
• Add a new method reportDistinctKeysSet in LeafNode
• Override reportDistinctKeysSet in datasource v2 relation
• Propagate reportDistinctKeysSet at DistinctKeysVisitor

Why are the changes needed?

Datasource v2 can be used to connect to some databases who support unique key.

Spark catalyst optimizer support do further optimization through distinct keys. So it can improve the performance if the Scan reports its distinct keys to Spark.

We already have several optimizer rules for distinct keys, for example:

• https://github.com/apache/spark/pull/35779
• https://github.com/apache/spark/pull/36117
• https://github.com/apache/spark/pull/36530

We also have some prs which is in progress related distinct keys, for example:

• https://github.com/apache/spark/pull/37267
• https://github.com/apache/spark/pull/36180

Does this PR introduce any user-facing change?

yes, a new interface added for developer

How was this patch tested?

add test

[ulysses-you]

cc @cloud-fan @sigmod @wangyum

[ulysses-you]

cc @cloud-fan @huaxingao if you have time to take a look, thank you

[github-actions[bot]]

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