[YUNIKORN-2323] Gang scheduling user experience issues

[manirajv06]

What is this PR for?

Send event for every ph allocation and also final event to convey "gang reseravtions has been done" to driver pod.

What type of PR is it?

• [ ] - Improvement

Todos

• [ ] - Task

What is the Jira issue?

https://issues.apache.org/jira/browse/YUNIKORN-2323

How should this be tested?

Screenshots (if appropriate)

Questions:

• [ ] - The licenses files need update.
• [ ] - There is breaking changes for older versions.
• [ ] - It needs documentation.