DelimitedInputFormat doesn't support the multi-character delimiter which is supported by DelimitedParser

[jihoonson]

Affected Version

0.17.0 and master

Description

The behavior of DelimitedInputFormat is different from the DelimitedParser in supporting multi-character delimiter. It currently uses the first character as its delimiter if the given delimiter has multiple characters. This behavior should be fixed to match with the behavior of DelimitedParser.

[jon-wei]

Fixed by #9199