soroban-cli: move config * commands to top level

[leighmcculloch]

I think we should consider moving the commands that live under soroban config to the top level.

i.e.:

config identity => key (assuming #1053)
config network => network

The network and identity commands are buried under config which makes them hard to find. They're important concepts that devs need to access regularly.

We should bury things under config if they're a set once and forget type of thing.

In reality devs need to interact with keys frequently. And likely need to switch and use multiple networks frequently too.

[willemneal]

True, the subcommand doesn't add much value, and soon we'll need a network start which definitely should be at the top level.