Deprecate winter.controller annotation

[mofr]

Is your feature request related to a problem? Please describe. The annotation is functionally unnecessary and should be removed avoid reduce clutter in the code.

Describe the solution you'd like Any class method with winter route should be able to act as an endpoint.

Additional context The following code should work fine

import winter

# No winter.controller here
class HelloWorldAPI:
    @winter.route_get('/hello/')
    def hello(self) -> str:
        return 'Hello, world!'

Probably the next step would be to allow routing free functions without classes.