How do I delete my iCloud.com email address?

I have been using an iCloud.com email address since I started using Apple devices many years ago. That was my login for my Apple ID as well as the email address that I used. I have decided instead to start using gmail.com as my email address. I know you can use a gmail.com email address as your Apple Account ID so I added my gmail.com email address to my Apple Account and made it my primary email address instead of my iCloud.com email address. I have an outlook.com email address that I made my notification email address. Now when I log into iCloud or any apps such as Game Center, Messages, and FaceTime I use my gmail.com.

My question, my iCloud.com email address is mostly spam these days and I no longer use it to communicate with anyone or for anything else. I'd like to simply get rid of it. Is this possible? I have heard of people just using a gmail.com email address for their iCloud login but does that mean they don't have an iCloud.com email address? Is it possible to simply not have one? Or does everyone who has an Apple Account even if they use gmail.com as their Apple Account email still have an iCloud.com email address? I definitely don't want to use it anymore so would like to get rid of my iCloud.com email address but of course do not want to close my Apple Account. Is this possible?

I know recently Apple began giving the option to change iCloud.com email addresses. In a worse case I'll simply change it so that the old iCloud.com email address is no longer there but since I won't use it I won't give it out to anyone.