Add remote proxy support to AH Polkadot&Kusama

[bkchr]

This adds remote proxy support to AssetHub on Polkadot and Kusama. Currently it is configured only to support using proxies registered on the relay chain to work on AssetHub. In the future this can be expanded.

[xlc]

this is not in polkadot-sdk repo so how do we want to test it on westend?

[bkchr]

this is not in polkadot-sdk repo so how do we want to test it on westend?

I will also port it there. I wanted to include it in the next release if possible. People are having more and more these problems of proxies not being on AH and similar. This pallet could solve the issue without requiring a root referendum (we already had one and another is prepared AFAIK).

[acatangiu]

I'd be more comfortable if we also did a security audit for this before adding it to live Polkadot AssetHub

[bkchr]

I'd be more comfortable if we also did a security audit for this before adding it to live Polkadot AssetHub

The scope of the changes is quite narrow. Doing some proper review should be fine. The only difference to the real proxy pallet is that the data is coming in from the outside.