[kbn/dev-utils] add RunWithCommands utility

[spalger]

As a part of moving the es-archiver to a more modern place I'd like to add a @kbn/dev-utils helper that uses many of the features of the run() helper, but with support for subcommands.

For an example of how this API works checkout the implementation I'm working on for my next PR here: https://github.com/spalger/kibana/blob/implement/es-archiver-package/packages/kbn-es-archiver/src/cli.ts

The gist of the feature is this:

import { RunWithCommands } from '@kbn/dev-utils'

new RunWithCommands({
  description: '...',
  globalFlags: { ... }, // same options as `run(..., { flags })`
})
  .command({
    name: 'foo',
    description: '...',
    flags: { ... }, // custom flags per command
    async run() {
      // ... do something when the "foo" command is executed ...
    }
  })
  .execute()

This helper replicates most of the functionality that we previously used commander for, and does it in a way that is async friendly, handles unexpected argument correctly, is type safe, and produces helpful documentation with --help or node scripts/xyz help foo.

top level help:

command specific help:

[elasticmachine]

Pinging @elastic/kibana-operations (Team:Operations)

[kibanamachine]

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@elasticmachine merge upstream

[brianseeders]

LGTM

async > streams for this