trie: iterate values pre-order and fix seek behavior

[roysc]

Proposed fix for #27837

[rjl493456442]

i think it's a valid fix, could you please add more relevant unit tests?

[roysc]

In order to properly change the order of traversal, I added a fix that will jump to the full node's leaf first, then back to iterate its child nodes normally, and skip the leaf at the end. It's a little funky, but seems to work fine.

I updated the unit tests to reflect the new ordering, which should sufficiently cover the behavior change. I also added an explicit case to check that seeking does not produce a leaf whose key prefixes the target key.

[roysc]

Is there anything else this needs?

[rjl493456442]

Wrt the path comparison, I think for ethereum state trie, this issue will never occur because of the same key length.

[roysc]

Right, I tried to acknowledge that in the issue (#27837 (comment)) - it won't show up in normal Geth operations, but it creates this inconsistency between a pre-order traversal of nodes vs. post-order traversal of values. I think it's at least worth documenting if not fixing.