Mostly it's about Go 1.22+ syntax with ranging over integers, but it also
prefers ranging over slices where possible (it makes code a little better to
read).
Notice that we have a number of dangerous loops where slices are mutated
during loop execution, many of these can't be converted since we need proper
length evalutation at every iteration.
Signed-off-by: Roman Khimov <roman@nspcc.ru>
We need to copy the result of `TryGet` method, otherwice the slice can
be modified inside `Add` or `Update` methods, which leads to
inconsistent MPT pool state.
In this commit:
1. Request unknown MPT nodes from peers. Note, that StateSync module itself
shouldn't be responsible for nodes requests, that's a server duty.
2. Do not request the same node twice, check if it is in storage
already. If so, then the only thing remaining is to update refcounter.
