* Unit tests update, code cosmetics
* Fix segfault with zombie handling
why:
In order to save memory, the data records of zombie entries are removed
and only the key (aka peer node) is kept. Consequently, logging these
zombies can only be done by the key.
* Allow to accept V2 payload without `shanghaiTime` set while syncing
why:
Currently, `shanghaiTime` is missing (alt least) while snap syncing. So
beacon node headers can be processed regardless. Normal (aka strict)
processing will be automatically restored when leaving snap sync mode.
* Extract RocksDB timing tests from snap unit tests as separate module
why:
Declutter, make space for more snap related unit tests.
* Renamed `undumpNextGroup()` => `undumpBlocks()`
why:
Source file name is called `undump_blocks.nim` which should be sort
of in sync with the method name(s).
* Implement snap/1 server method `getByteCodes()`
* Implement snap/1 client method `getByteCodes()`
* Implement faculty for handling contract code fetching via snap/1
* Provide persistent storage for contract code records
* Implement contract code snap sync fetch & store
* Code massage, cosmetics
* Unit tests for verifying snap sync snapshot dump
details:
Use `undump_kvp.dumpAllDb()` to dump any database.