Move proxies migration (#7205)

* move the time delayed proxies migration into a separate function

* add use statement

* Update frame/proxy/src/lib.rs

* bump proxy cargo version

* update Cargo.lock

* Update lib.rs

* better format

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>
Co-authored-by: Gav Wood <gavin@parity.io>