Support components implementing cli sub-commands

## Problem Statement

Currently in a component's component.yaml, it can only define top level commands without sub-commands or a hierarch

So if I want to implement

`dpm create new` / `dpm create new application` `dpm create new component`

I could only define `dpm create` in my component.yaml, and all the sub-sequence sub-commands I would have to implement opaquely in my components.

Instead,, let's have the component.yaml define not just the parent level command, but also the available sub-commands.

NOTE : this will complicate the checks that alternative components do not try to stomp on each other by implementing competiting subcommands

i.e. --> there may be two components they try to implement `dpm codegen js` --> one by taking ownership of the root `dpm codegen` namespace and one by explicitly writing `dpm codegen js` and `dpm codegen java` sub-commands

### Checklist

- [ ] Modify the existing `component.yaml` schema to allow name field (which represents the actual command string used) to be a list
- [ ] Modify the assembler to output a tree of commands instead of a list of commands
- [ ] Tests
- [ ] Docs

Start with the existing component.yaml schema and assembler, then trace how command ownership conflicts are checked. Cover nested command declarations and root-versus-subcommand collisions in tests, and update the documentation; done means commands such as dpm create new application can be declared and assembled without ambiguous ownership.

Written by the indexing model from the issue text.