Increase state sync retries

[nazar-pc]

It wouldn't hurt doing more attempts, but might help some users. Looks like large genesis state makes it difficult for some users to download it an situation will only get worse over time.

Code contributor checklist:

• I have read, understood and followed contributing guide

[liuchengxu]

Perhaps the proposal in polkadot-fellows/RFCs#112 can be considered to improve the state sync performance for the short term. The patch is super simple if we don't take the backward compatibility into account (not sure if it's too late for network breaking changes though), just a few change lines liuchengxu/polkadot-sdk@2556fef, but the improvement is significant.

[nazar-pc]

Yes, I'm following that proposal and already considered patching out fork. We just launched mainnet though, so we'll have to have some sort of compatibility layer.