Improve rescan and recovery UX

[notnout]

Current UX to recover the funds from a wallet with old channels is very frustrating and there are some low hanging fruit improvements that could be made to notable reduce the pain inflicted on the users.
This is based on the recent experience recovering funds in collaboration with the Breez support and development team (so folks from Breez team have more details/specifics).

Here are specific changes that would make the experience much less painful:

• From the dialog that my channels are closed there should be a direct button/action to do the next step.
• Add a simple message for how much data/time do you expect this to take. Literally just add that label and the UX would be 50% better.
• The Breez blockchain synchrozination dialog should show some finer grained progress (small "xx kB/s" would be great, or whatever it is, block height, timestamp…)
• Fix the ability to retry/reconnect and continue downloading the chain from where it left (not having to restart every time)
• Do not require the app to be in the foreground.
• Fix whatever is causing the "Breez is offline" while I'm provably online. Or update messaging to be accurate.
• If the wallet doesn't have any working channel, then don't let the user create invoices that will inevitably fail. Error labels/messages are super important.
• If there are 120 minutes worth of stuff that needs to happen after syncing the blockchain reaches 100%, then include it in the %. Don't let the user guess the time. Especially if the actual process takes longer than additional 120 minutes.
• Consider implementing a feature that keeps the phone on for long running tasks (on Android there are apps that do this, so it's possible). Sidenote: Breez should sync the chain regularly (e.g. Phoenix Wallet wakes up once a day to do this).
• Write documentation page to handle this situation. Add options like the ways to keep the app running without having to touch it every 10 mins (like using Caffeine - but be careful about linking another app…). Add estimates for the download size, etc. Add troubleshooting section. This would reduce the number of support cases you need to handle.