Check db indexes for in-order insertions

[Arkenan]

Some db insertions in libmdbx are theoretically better if they are in order, specially if they are big batch insertions (e.g. on sync or block imports). We should measure if there are improvements in some examples by changing the indexing of the tables to something that can be in-order when batch-inserting, or if just sorting the elements by their index before inserting them.