Implement node-less restore process (for desktop and mobile)

[sasha-abramovich]

As @valdok noticed, for successful restore only UTXO set and the first header+chainwork proof should be downloaded. The rest of headers and kernels are not required.

Lighter restore process can make mobile restore simpler (and consuming less battery power).

[sasha-abramovich]

@valdok @gingervik reminder about what we've mentioned during the dev meeting: when a wallet connects to the node, it should know whether a node supports this restore functionality and if the node does support restore, clear and human readable reporting about the all the restore process errors should propagate to the wallet.

[sasha-abramovich]

also, can client please ask the expected file size from the restore server or whatever? this is to avoid redundant download and also to inform the user as file size might affect his data plan. @valdok @gingervik @BigRomanov

[sasha-abramovich]

one more thing please: when the node is downloading the files it's better to have an API that will inform the mobile regarding the progress of forming/updating the files.

if you guys want me to open separate tasks - just tell.

[sasha-abramovich]

Following discussion with @gingervik, this task is moved to the next sprint, where my functional requests might be considered.

[gingervik]

checked with ios build