Don't test more than MinGapLimit clean keys during resync

[turbolay]

After merge of TurboSync, there will be one last problematic case for wallet synchronization: Resyncing or recovering from file a big wallet.
It's currently a problem because when testing thousands of derived keys against the whole blockchain history, one will find hundreds of false positives blocks to download.
And it's in fact completely avoidable by taking a simple step: Never test more than MinGapLimit clean keys.

Let's say I resync from Height: 0 with a Wallet.json file containing 10.000 keys and MinGapLimit: 21.
Currently, all 10.000 keys will be tested against the whole blockchain history, which is useless: We could only test the first 21 keys , until we find a TX, then we test keys from 2 to 22, then 3 to 23..... etc...

One alternate way to do it is to "underive" the keys but store their label, then apply the labels back when sync is finished.

[turbolay]

What does this assignment mean? That we want it for 2.0.7?

[MaxHillebrand]

What does this assignment mean? That we want it for 2.0.7?

It's not in the 2.0.7 milestone, so no.

[turbolay]

This issue is still relevant and should be fixed, however I'm closing it as it will not be worked on in a foreseeable future