Organize etcdctl commands and add more documents

[ah8ad3]

What would you like to be added?

I want commands of etcdctl to be organized and documented in a better way.

1. For organizing i suggest to remove nested part of commands for example instead of having this:

        user add                Adds a new user
        user delete             Deletes a user
        user get                Gets detailed information of a user
        user grant-role         Grants a role to a user
        user list               Lists all users
        user passwd             Changes password of user
        user revoke-role        Revokes a role from a user

We can do something like this:

      Basic KV commands:
        del                  Removes the specified key or range of keys [key, range_end)
        get                  Gets the key or a range of keys
        put                  Puts the given key into the store

      Management Commands:
        user                  User related commands
        role                  Role related commands

And rest of this for other commands.

2. For documenting i suggest to make the documents and help texts for commands better and more helpful throw some examples and define better.
   For example when we invoke etcdctl leahe -h we get

NAME:
        lease - Lease related commands

USAGE:
        etcdctl lease <subcommand> [flags]

Maybe we can do something like this:

NAME:
        lease - Lease related commands

Description:
        Leases in etcd act as timers for data, automatically deleting keys when their associated lease expires.

USAGE:
        etcdctl lease <subcommand> [flags]

        etcdctl lease grant 60   # Creates a lease that lasts 60 seconds

        etcdctl lease keep-alive <lease_id> --once # Resets the keep-alive time to its original value and cobrautl.Exits immediately

Add a one line description so new users can understand what it is without going and searching for what is the lease, it's a tradeoff we don't want to throw the whole document here just a little sip of what is it.
And put some popular usages in the USAGE section would be nice too.

Why is this needed?

As a newcomer to etcdctl it was hard for me to understand what it does at first, i was constantly searching the websites for commands to understand some of it. To enhance user experience, I propose implementing measures to clarify command functionalities upfront, easing the learning curve.

Also i think the first view of etcdctl -h is a little bit crowded and i believe with removing some subcommands that are not necessarry to show at first and style it a little bit this way users are greeted with a more intuitive interface.

[ah8ad3]

I want to get more involve in etcd community and i think with this issue i can help to make etcdctl better and also understand the basics and hopefully start working on core of etcd. If team approves, i would like to define some tasks and start working on this issue.

[ah8ad3]

/area documentation
/area etcdctl