Introduce lightning connect

[tchaton]

What does this PR do?

This PR introduces logic to connect to an application. The connect, disconnect acts as a context manager and makes the App Commands available.

Here is the user flow:

(.venv) ➜  lightning --help
Usage: lightning [OPTIONS] COMMAND [ARGS]...

Options:
  --version  Show the version and exit.
  --help     Show this message and exit.

Commands:
  connect     Connect to a Lightning Application.
  create      Create Lightning AI self-managed resources (clusters, etc…)
  delete      Delete Lightning AI self-managed resources (clusters, etc…)
  disconnect  Disconnect to a Lightning Application.
  init        Init a Lightning App and/or component.
  install     Install a Lightning App and/or component.
  list        List Lightning AI self-managed resources (clusters, etc…)
  login       Log in to your lightning.ai account.
  logout      Log out of your lightning.ai account.
  run         Run a Lightning application locally or on the cloud.
  show        Show given resource.

(.venv) ➜  lightning connect example
The Lightning App `example` provides a client interface (CLI). Do you want to proceed and install its CLI ? [y/N]: y
 
Storing `command_with_client` under /Users/thomas/.lightning/lightning_connection/commands/command_with_client.py
You can review all the downloaded commands under /Users/thomas/.lightning/lightning_connection/commands folder.
 
The client interface has been successfully installed. 
You can now run the following commands `lightning ['command_without_client', 'command_with_client', 'nested_command']`.
 
You are connected to the cloud Lightning App: example.

(.venv) ➜   lightning --help         
You are connected to the cloud Lightning App: example.
Usage: lightning [OPTIONS] COMMAND [ARGS]...

  --help     Show this message and exit.

Lightning App Commands
  nested_command         Description
  command_without_client Description
  command_with_client    Description

(.venv) ➜   lightning command_with_client --help
You are connected to the cloud Lightning App: example.
usage: command_with_client [-h] [--name NAME]

optional arguments:
  -h, --help   show this help message and exit
  --name NAME

(.venv) ➜  lightning command_with_client --name=hello
You are connected to the cloud Lightning App: example.
Your command execution was successful.

(.venv) ➜   lightning disconnect                      
You are disconnected to the cloud Lightning App: example
.

(.venv) ➜   lightning disconnect
You aren't connected to any Lightning App. Please, use `lightning connect app_name_or_id` to connect to one.

(.venv) ➜  lightning connect localhost
You are connected to the local Lightning App.

Fixes #<issue_number>

Does your PR introduce any breaking changes? If yes, please list them.

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cc @Borda

[tchaton]

Looks good, let’s make sure this work plays nicely with auth.
Basically users would have to first login on the CLI and then connect to an app via the id or url. The next time around, the connect file is still there but I am not authenticated, so we should make sure we communicate the user that we first need to log in.

Sounds great. I will add this when auth is ready on the infra side. Should be simple on the CLI side.

[Borda]

Missing chlong entry, but let's do one more pass on fixing all other missing entries before release...