[MINOR][DOCS] Use multi-line JavaDoc comments in Scala code.

[dongjoon-hyun]

What changes were proposed in this pull request?

This PR aims to fix all Scala-Style multiline comments into Java-Style multiline comments in Scala codes.
(All comment-only changes over 77 files: +786 lines, −747 lines)

How was this patch tested?

Manual.

[dongjoon-hyun]

Could you review this PR, @rxin ?

[SparkQA]

Test build #54770 has finished for PR 12130 at commit 9c06d60.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[dongjoon-hyun]

org.apache.spark.sql.execution.streaming.state.StateStoreSuite.maintenance failure again.
It's a timeout error, should we increase the timeout for the test?

[dongjoon-hyun]

Rebased to trigger Jenkins test.

[SparkQA]

Test build #54779 has finished for PR 12130 at commit 51ab3ba.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[SparkQA]

Test build #2734 has finished for PR 12130 at commit 51ab3ba.

• This patch passes all tests.
• This patch merges cleanly.
• This patch adds no public classes.

[rxin]

Thanks - merging in master.

[rxin]

BTW in the future for changes this size we should create a JIRA ticket.

Can you look into whether it is possible to create a scalastyle rule for this so we don't do the scaladoc style docs in the future?

[dongjoon-hyun]

Thank you, @rxin . I see. I'll create a JIRA for large size patch .
And, for creating new ScalaStyle rule to enforce this seems a good idea.
I'll take a look at that tomorrow. Thanks again.

[dongjoon-hyun]

Hi, @rxin .
I made a new PR for ScalaStyle rule enforcement ( #12221 ).