Generate indented toml config files for improved legibility

[RickiNano]

The current config layout is quite hard to navigate.
This PR adds indentation to clearly show what is a child object of a node. Indentations are allowed for the TOML format according to the official documentation.
--generate_config cli command has been tested with both node, rpc and log configs. It also supports the --use_defaults command with correct output.
Here is a small sample of the new config file for illustration:

[node.httpcallback]

        # Callback address.
        # type:string,ip
        # address = ""

        # Callback port number.
        # type:uint16
        # port = 0

        # Callback target path.
        # type:string,uri
        # target = ""

[node.ipc.flatbuffers]

        # Allow client to send unknown fields in json messages. These will be ignored.
        # type:bool
        # skip_unexpected_fields_in_json = true

        # Verify that the buffer is valid before parsing. This is recommended when receiving data from untrusted sources.
        # type:bool
        # verify_buffers = true

[node.ipc.local]

        # If enabled, certain unsafe RPCs can be used. Not recommended for production systems.
        # type:bool
        # allow_unsafe = false

        # Enable or disable IPC via local domain socket.
        # type:bool
        # enable = false

        # Timeout for requests.
        # type:seconds
        # io_timeout = 15

        # Path to the local domain socket.
        # type:string
        # path = "/tmp/nano"

[node.ipc.tcp]

        # Enable or disable IPC via TCP server.
        # type:bool
        # enable = false

        # Timeout for requests.
        # type:seconds
        # io_timeout = 15

        # Server listening port.
        # type:uint16
        # port = 7077

[pwojcikdev]

Do we really want to do it? Some time ago I researched a similar approach and was discouraged after reading through toml-lang/toml#608 especially since most tools should offer pretty good toml syntax highlighting.

[RickiNano]

The TOML language is not that widespread. Even notepad++ that supports 50+ languages doesn't come with a toml parser.
I prefer it to be indented. It makes it super easy to read no matter what text editor you are using.

[pwojcikdev]

Okay, without a syntax highligher indentation definitely helps.