[chain] Standardize node directory structure

[zivkovicmilos]

Description

Master issue: #1836

This issue concerns standardizing the node directory structure, after #1605 and #1593.
After internal discussions with @thehowl, we've come to the conclusion that the following structure would be more than enough for supporting future gno functionality:

.
├── genesis.json
└── my-node-dir/
    ├── db/
    │   ├── blockstore.db (folder)
    │   ├── gnolang.db (folder)
    │   ├── state.db (folder)
    │   └── cs.wal
    ├── secrets/
    │   ├── priv_validator_state.json
    │   ├── node_key.json
    │   └── priv_validator_key.json
    └── config/
       └── config.toml

The definition of done for this task:

• gnoland secrets init initializes the data directory as shown (<default-node-dir>/secrets)
• gnoland config init initializes the config.toml as shown (<default-node-dir>/config.toml)
• the genesis.json lives outside the node directory

The reason for having genesis.json live outside the node directory, and config.toml inside is the following:

• genesis.json is required for a running node, it's something that should always be provided and immutable
• config.toml is not required, and if it's not given, it should assume defaults (defaults can't be assumed for the genesis configuration)