* CoreDB: Re-org API
details:
Legacy API internally uses vertex ID for root node abstraction
* Cosmetics: Move some unit test helpers to common sub-directory
* Extract constant from `accouns_cache.nim` => `constants.nim`
* Fix tracer methods
why:
Logger dump data were wrongly dumped from the production database. This
caused an assert exception when iterating over the persistent database
(instead of the memory logger.) This event in turn was enabled after
fixing another inconsistency which just set up an empty iterator. Unit
tests failed to detect that.
* Aristo: remove obsolete functions
* Aristo: Fix error code for non-available hash keys
why:
Must not return `not-found` when the key is not available (i.e. the
current changes were not hashified, yet.)
* CoreDB: Provide TDD and test framework