[Feature][Seatunnel-web]Add support to configure placeholder with default value in the job config.

[arshadmohammad]

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/seatunnel/tree/dev/docs

[arshadmohammad]

The primary modification in this Pull Request focuses on org.apache.seatunnel.app.utils.JobUtils#replaceJobConfigPlaceholders and its application.

I am currently encountering an issue when ${configParam:default} is set in the job configuration.
The ConfigFactory.parseString(jobConfigString) operation fails with the error:
String: 1: Token not allowed in path expression: ':' (you can double-quote this token if you really want it here).

I plan to investigate the variable substitution implementation on the Seatunnel engine side.

[arshadmohammad]

Executed integration tests, all are passed

Manually tested conditional query

[Hisoka-X]

LGTM. Thanks @arshadmohammad !

[arshadmohammad]

Thanks @Hisoka-X for reviewing and merging the PR.