* Remove 32bit os support from `custom_network` unit test
also:
* Fix compilation annoyance #1648
* Fix unit test on Kiln (changed `merge` logic?)
* Hide unused sources do not compile
why:
* Get them out of the way before major update
* Import and function prototype mismatch -- maybe some changes got out
of scope.
* Re-implemented `db_chain` as `core_db`
why:
Hiding `TrieDatabaseRef` and `HexaryTrie` by default allows to replace
the current db wrapper by some other one, e.g. Aristo
* Support compiler exception warnings for CoreDbRef base methods.
* Allow `pairs()` iterator on all memory based key-value tables
why:
Previously only available for capture recorder.
* Backport `chain_db.nim` changes into its re-implementation `core_apps.nim`
* Fix exception annotation
322f1c2e9e