UX: Direct users to Unstake / Leave Pool if Remove Bond == full bond amount

[rossbulat]

The Bond management system does not assume users wish to completely exit their staking position, maintaining a minimum of 250 DOT for nominators and 1 DOT for pools. This can be confusing for stakers who want to completely exit their positions.

We should amend the UI to:

• Add an additional prompt asking whether the user wants to completely unstake, and provide a link to open the Unstake / Leave Pool modal, directly from "Remove Bond".