[11.x] Implement Key Rotation Functionality in KeyGenerateCommand

[SamAsEnd]

This pull request introduces the ability to rotate application keys in the Laravel environment file. The --rotate option has been added to the key:generate command. When this option is used, the current application key is added to a list of previous keys stored in the APP_PREVIOUS_KEYS environment variable, and a new application key is generated.

This feature is inspired because of @taylorotwell Laracon EU 2024 presentation.
We can now pass --rotate on the key:generate command.

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If possible, please consider releasing your code as a package so that the community can still take advantage of your contributions!

If you feel absolutely certain that this code corrects a bug in the framework, please "@" mention me in a follow-up comment with further explanation so that GitHub will send me a notification of your response.