Enable maintainer-owned code ownership within the kgateway project

[lgadban]

As we are significantly increasing velocity in the kgateway project, it is becoming more apparent that we need to evolve in order to enable quick delivery of user requests while still maintaining a high quality of changes.

The vast majority of the work being done is in the kgateway controller and we currently have just a single maintainer group responsible for all approvals of this very broad component.

Ideally we can expand into a more advanced form of project management and collaborations.
Some of the goals are to:

• Allow maintainers to be organized into various areas of ownership throughout the codebase
  • These groups (and their membership) change semi-frequently and should not require a process-heavy procedure to change
• Have a large group of active maintainers while allowing folks to specialize in certain areas
• Encourage and delegate ownership of components to SMEs
• Ensure changes to critical components of the codebase can only be approved by maintainers that are familiar with the inner-workings of kgateway

#138 is intended as a stopgap solution to allow us to start splitting out the responsibilities of code approvals into more specific groups of maintainers.
However, a simple file-based CODEOWNERS approach does not get us much closer to the goals listed above.

Ideally the maintainers group (as defined by community process) should be able to own this process wholly, not requiring time-intensive and process-heavy community governance.

[lgadban]

One option that seems to be a good fit would be to use https://github.com/jpmcb/prow-github-actions with a base group of ownership defined as a community org.