Integrate Lite launcher into Lightning CLI

[awaelchli]

What does this PR do?

This PR changes the Lite CLI from argparse to click to be integrated into the main lightning CLI. Originally we though we can wrap the argparse CLI into click, but this doesn't work well. The simple solution seems to be the best. The click package has no dependencies.

lightning run --help

Usage: lightning run [OPTIONS] COMMAND [ARGS]...

  Run a Lightning application locally or on the cloud.

Options:
  --help  Show this message and exit.

Commands:
  app   Run an app from a file.
  lite  Run a Lightning Lite script.

The lite subcommand is only available if lightning-lite is installed. The name here is not final, it remains to be decided.

Before submitting

• Was this discussed/approved via a GitHub issue? (not for typos and docs)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure your PR does only one thing, instead of bundling different changes together?
• Did you make sure to update the documentation with your changes? (if necessary)
• Did you write any new necessary tests? (not for typos and docs)
• Did you verify new and existing tests pass locally with your changes?
• Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

PR review

Anyone in the community is free to review the PR once the tests have passed.
Before you start reviewing make sure you have read Review guidelines. In short, see the following bullet-list:

• Is this pull request ready for review? (if not, please submit in draft mode)
• Check that all items from Before submitting are resolved
• Make sure the title is self-explanatory and the description concisely explains the PR
• Add labels and milestones (and optionally projects) to the PR so it can be classified

Did you have fun?

I made sure I had fun coding 🙃

cc @Borda @carmocca @justusschock @awaelchli

[tchaton]

Looks great ! Should we support lightning run model --cloud