* Update nearby/neighbour leaf nodes finder
details:
Update return error codes so that in the case that there is no more
leaf node beyond the search direction, the particular error code
`NearbyBeyondRange` is returned.
* Compile largest interval range containing only this leaf point
why:
Will be needed in snap sync for adding single leaf nodes to the range
of already allocated nodes.
* Reorg `hexary_inspect.nim`
why:
Merged the nodes collecting algorithm for persistent and in-memory
into a single generic function `hexary_inspect.inspectTrieImpl()`
* Update fetching accounts range failure handling in `rangeFetchAccounts()`
why:
Rejected response leads now to fetching for another account range. Only
repeated failures (or all done) terminate the algorithm.
* Update accounts healing
why:
+ Fixed looping over a bogus node response that could not inserted into
the database. As a solution, these nodes are locally registered and not
asked for in this download cycle.
+ Sub-optimal handling of interval range for a healed account leaf node.
Now the maximal range interval containing this node is registered as
processed which leafs to de-fragementation of the processed (and
unprocessed) range list(s). So *gap* ranges which are known not to
cover any account leaf node are not asked for on the network, anymore.
+ Sporadically remove empty interval ranges (if any)
* Update logging, better variable names
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