* Temporarily pin trie to #2
* Use generic and delay trait object casting
Rust does not support super-trait upcasting
* Add PlainDB impl for Ephemeral
* Add PlainDB trait alias for completeness
* Use PlainDB for test TrieBackendStorage fetch
We always check overlay first for a storage fetch, which already checked null data. Using PlainDB here makes it work
nicer with other PlainDB overlays.
* Update trie reference
* Use HashDBRef in places when approriate
* Use PlainDBRef in places when approriate
* Update trie crate reference
* Remove unused HashDB::keys
* Patch dependencies
* Fix cargolock
* Update cargo lock again