[SPARK-30554][SQL] Return Iterable from FailureSafeParser.rawParser

[MaxGekk]

What changes were proposed in this pull request?

Changed signature of rawParser passed to FailureSafeParser. I propose to change return type from Seq to Iterable. I took Iterable to easier port the changes on Scala collections 2.13. Also, I replaced Seq by Option in CSV datasource - UnivocityParser, and in JSON parser exception one place in the case when specified schema is StructType, and JSON input is an array.

Why are the changes needed?

Seq is unnecessary requirement for return type from rawParser which may not have multiple rows per input like CSV datasource.

Does this PR introduce any user-facing change?

No

How was this patch tested?

By existing test suites JsonSuite, UnivocityParserSuite, JsonFunctionsSuite, JsonExpressionsSuite, CsvSuite, and CsvFunctionsSuite.

[MaxGekk]

@HyukjinKwon @srowen Please, review this PR.

[srowen]

Seems OK; is it just some code polish or does it make an impact on performance?

[MaxGekk]

@srowen Main goal is code polish. Potentially, it could improve performance slightly because Seq builder is slower than Option.

[SparkQA]

Test build #116956 has finished for PR 27264 at commit 1f7d9fd.

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

[SparkQA]

Test build #116964 has finished for PR 27264 at commit 04d8194.

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

[MaxGekk]

jenkins, retest this, please

[SparkQA]

Test build #117002 has finished for PR 27264 at commit cf5ab4e.

• This patch fails from timeout after a configured wait of 400m.
• This patch merges cleanly.
• This patch adds no public classes.

[MaxGekk]

jenkins, retest this, please

[SparkQA]

Test build #117011 has finished for PR 27264 at commit cf5ab4e.

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

[MaxGekk]

jenkins, retest this, please

[SparkQA]

Test build #117014 has finished for PR 27264 at commit cf5ab4e.

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

[SparkQA]

Test build #117015 has finished for PR 27264 at commit cf5ab4e.

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

[HyukjinKwon]

Thanks @MaxGekk for addressing my comment.

Merged to master.