### 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`.
Closes#27264 from MaxGekk/failuresafe-parser-seq.
Authored-by: Maxim Gekk <max.gekk@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
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