Token lists: balances may be loaded too long + lists are jumping when loaded

[anxolin]

1. Sometimes, a pop-up may appear above the swap section when connect a wallet in xDAI (see 5-6 sec on the video below):
   https://images.zenhubusercontent.com/192335743/a37001d3-9ea3-4116-966d-89c4b6a53729/xdai.mp4

2. Balances may be loaded too long after a wallet connection/page reload (see the video above).

3. Token lists are jumping after balances are loaded. It causes some inconveniences in selecting tokens, especially in mobile devices
   https://drive.google.com/file/d/1317O3X9HWkQVnQ1SQf8RzV7z4jvdXMn7/view

Expected: show a loader in the list until all balances are loaded?

Original issue gnosis/cowswap#1061 by @elena-zh

[elena-zh]

Fixed in 1.21