Consolidate the way `dxns` commands are working

[rzadp]

• generating address should store it in halo
• dx halo should print current profile
• verbs
• persistence mechanisms should work the same way - "default" files are different - one is a symlink
• Remove "normal connection closure" from the log
  • Also some similar logs which happen when the connection to Polkadot API is opened and closed too quickly
• A single command to print all stuff - profiles, addresses, accounts
• Migrate docs from Device credentials dxos#860 and readmes to docs
• Should be able to override address selection by command line parameter, just as account currently
  • Account - DX_DXNS_ACCOUNT
  • Address - DX_DXNS_ADDRESS
• Rename dx ns list to dx ns info