[7.x] Add full MySQL enum support

[nuernbergerA]

Follow-up from #32205

Now we can rename, change, extend enum columns in MySQL.

Current State

If you rename an enum column it will turn into string without any constraint.

Personally I don't see a use-case for enum outside of MySQL, because in other SQL implementations it adds a constraint to a string witch comes with performance costs.

MySQL on the other side gains performance.

Future

Maybe we should also consider dropping enum support for Non-MySQL in general.

[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.

[nuernbergerA]

@taylorotwell some explanation why?

If you won't merge this in we should at least throw an exception if you try to rename/change an enum.

What are your thoughts on that?

[mnabialek]

I'm also curious. I often work with tables that have enum and it's really hard to use migrations in those tables at the moment.