Add leader election to the custom controller

[Kalaiselvi84]

Is your feature request related to a problem? Please describe.
The absence of leader election in the custom controller example leads to potential conflicts.

Describe the solution you'd like
I would like to incorporate leader election into the custom controller example to ensure that only one controller assumes the responsibility of managing/watching the gameserver.

Additional context
Log - https://gist.github.com/Kalaiselvi84/c5a576edebd1cc1c1ae5481c827fed17