[Enhancement] XCM - show balances on assets list

[0byt]

From Fritz:
Asset transfer/ teleport: Additionally to the available chains that support the selected assets I would like to have the amount I have on each of those already displayed in the dropdown aswell. I feel thats handy if I just quickly want to get funds to my chain of interested I don't have to manually iterate through all of those trying to find the one which has enough balance for me to transfer. Especially with xcm being used more I think assets get split up wide and far so that this feature would allow for some more convenience.

[tien]

With the xcm library, available balance are currently lazily fetch once a route is selected. Can probably get the balance from our balances lib instead.

[0byt]

if we can, that would be helpful for the UX