This pull request preserves the root->ID mappings in the path database
even after the associated state histories are truncated, regardless of
whether the truncation occurs at the head or the tail.
The motivation is to support an additional history type, trienode history.
Since the root->ID mappings are shared between two history instances,
they must not be removed by either one.
As a consequence, the root->ID mappings remain in the database even
after the corresponding histories are pruned. While these mappings may
become dangling, it is safe and cheap to keep them.
Additionally, this pull request enhances validation during historical
reader construction, ensuring that only canonical historical state will be
served.
This is a internal refactoring PR, renaming the history to stateHistory.
It's a pre-requisite PR for merging trienode history, avoid the name
conflict.
