Add cache flag to the decorator.

[DavidZalevsky]

We should add a default flag that turns on/off (bypass) cache into a decorator.

Example:
@memoize(Cache("tlfu", 1000), timeout=timedelta(hours=1), lock=True, typed=False, cache_enabled=True)

Thanks to such a solution, if our production application uses the cache, then on the test environment, we can easily disable it with an environment variable in order to speed up testing.

[Yiling-J]

Thanks for the suggestion! How about setting the cache size to 0 instead of adding another parameter? I think this approach might already work, though there isn’t a test for it yet. However, even when the cache size is set to zero, currently the extra time wheel thread is still running, which can be optimized.