Protocol merging

[Galtozzy]

Try to see if we can merge protocols in case 2 or more decorators are being applied to a single function simultaneously.

Currently, the following is true:

@cached(key='test')
@once(key='test')
async def some_operation() -> str:
    return 'result'


await some_operation.reset()  # will be valid
await some_operation.is_locked()  # type checker will report an error

I think we can detect if the function decorator is being applied to the instance of something py-cachify provides and merge protocols.