clean up ncli_testnet and reduce ValidIpAddress usage

[tersec]

ValidIpAddress is requiresInit and isn't compatible with the design of either nim-serialization or nim-confutils:

type
  ValidIpAddress* {.requiresInit.} = object
    value: IpAddress

This addresses the non-beacon_chain/ parts which don't have to be compatible with beacon_chain/conf.nim.

It also does some other minor cleanup, e.g., some proc to func in ncli_testnet.

It bumps nim-confutils to pull in status-im/nim-confutils#94 (the only change).

[github-actions]

Unit Test Results

         9 files  ±0    1 092 suites  ±0   33m 43s ⏱️ + 2m 5s
  3 892 tests ±0    3 595 ✔️ ±0  297 💤 ±0  0 ❌ ±0 
15 973 runs  ±0  15 650 ✔️ ±0  323 💤 ±0  0 ❌ ±0 

Results for commit 0fa3829. ± Comparison against base commit 41dfc9e.