Rename OutputEventRequestState -> OutputRequestStateEvent

[heuer]

For all other events we use "Event" as Suffix (i.e. RequestStartDragEvent, KeyboardKeyEvent, TouchMotionEvent, …).

output.OutputEventRequestState should adapt that scheme.

Maybe deprecate it in the next subrelease and remove it in 0.19?

Or deprecate it in 0.18?

[heuer]

On further reflection, deprecation is difficult because pywlroots creates instances of the class, not the user.

We can use something like this:

class OutputRequestStateEvent(Ptr):
    # […]

OutputEventRequestState = OutputRequestStateEvent

to keep mypy etc. happy but I think it's not possible to warn users about the name change.