feat: Allow `pop` to update dependencies on demand

[al3mart]

Scenario

User is working on a patch for a polkadot-sdk runtime or similar where they need to point all the polkadot-sdk dependencies to a different repository, a concrete branch or something in those lines.
Either the user has a scrip, some regex help or vim macros to get this done quickly, or they will have to spend valuable time finding and updated all these dependencies.

Idea

It could be interesting to either integrate diener or in any other way allow for these flows to happen via pop.

Allowing users to update, for instance all polkadot-sdk specific dependencies with just a quick pop command.

[moliholy]

We can do that with psvm as well once paritytech/psvm#34 gets merged.

[al3mart]

I believe psvm won't allow us to point dependencies to my own fork of polkadot-sdk, for example.

[moliholy]

Yes, that could work. We'd have to transform diener into a library as well for that, but it's doable. However, IIRC psvm also updates satellite dependencies to the right versions, not just polkadot-sdk ones. And that will be very useful in a future with only the polkadot-sdk-umbrella dependency, which will obviously be very straightforward to change manually.

EDIT: just checked diener seems to be significantly less maintained than psvm 🤔