[Improve][connector-v2][FileSink] Allow the user to set the row delimiter as an empty string

[lightzhao]

If a user's text line is marked with a line delimiter, it is unnecessary to set the line delimiter, so set the line separator as an empty string

Purpose of this pull request

Check list

• Code changed are covered with tests, or it does not need tests for reason:
• If any new Jar binary package adding in your PR, please add License Notice according
  New License Guide
• If necessary, please update the documentation to describe the new feature. https://github.com/apache/incubator-seatunnel/tree/dev/docs
• If you are contributing the connector code, please check that the following files are updated:
  1. Update change log that in connector document. For more details you can refer to connector-v2
  2. Update plugin-mapping.properties and add new connector information in it
  3. Update the pom file of seatunnel-dist

[lightzhao]

@Hisoka-X @TyrantLucifer please review ，thanks.

[Hisoka-X]

LGTM

[lightzhao]

@TaoZex please review, thanks.

[lightzhao]

@Hisoka-X please review, thanks.

[lightzhao]

@TyrantLucifer PTAL, thanks.

[lightzhao]

@TyrantLucifer PTAL, thanks.

[TyrantLucifer]

IMO, This can lead to data disruption and lost data, when user sets a empty delimiter, all data will be wrote on one line. How can we read this type file in SeaTunnel? There may be 10 rows of data before writing and only 1 row after reading. cc @EricJoy2048 @CalvinKirs Hey guys, what do you think about it?

[lightzhao]

IMO, This can lead to data disruption and lost data, when user sets a empty delimiter, all data will be wrote on one line. How can we read this type file in SeaTunnel? There may be 10 rows of data before writing and only 1 row after reading. cc @EricJoy2048 @CalvinKirs Hey guys, what do you think about it?

This case is aimed at the fact that the user data already contains a newline symbol, which allows the user to set an empty action.

[lightzhao]

@EricJoy2048 @CalvinKirs PTAL.

[TaoZex]

Please incorporate the latest code changes in order to pass CI.