Update cachetools stubs to 5.0 #6953

Cachetools updated to 5.0.0 (https://github.com/tkem/cachetools/blob/master/CHANGELOG.rst#v500-2021-12-21) so the stubs should be updated to support that.

I also want to point out that some types are dependant on parameters. For instance, the TTLCache accepts a function for the timer, and the ttl should be something that can be added to the result of timer(). Currently it's float, but in the documentation, it could be timedelta if timer is set to datetime.now. I don't know if this should be split off into its own issue or just handled when upgrading the types.