Move "config" and "lang" to bot properties instead of middleware

[MasterGroosha]

As noted by aiogram maintainer, one can add custom properties which are meant to be constant (like config or lang) directly to Bot instance.
Currently these two properties are pushed to every new update in middleware, which is not performance-wise.

This way, the only middleware can be easily removed, simplifying the code a bit.

[MasterGroosha]

Fixed in aiogram3 branch, will be merged with master in future