[CLI] Handle unrecognized arguments

[un-def]

• All commands now reject unrecognized arguments

• Undocumented ${{ run.args }} for tasks and services is still supported but requires -- pseudo-argument:

  If you have positional arguments that must begin with -
  and don’t look like negative numbers, you can insert
  the pseudo-argument '--' which tells parse_args()
  that everything after that is a positional argument

  dstack apply --reuse -- --some=arg --some-option
                       ^^
  

Fixes: #3073

---

@peterschmidt85 not sure if we want to drop ${{ run.args }} altogether or document it as a feature.

[peterschmidt85]

@un-def
Was just testing dstack init and got an indirectly related question.

dstack init --help
Usage: dstack init [-h] [--project PROJECT] [-P REPO] [-t OAUTH_TOKEN] [--git-identity SSH_PRIVATE_KEY]

Options:
  -h, --help            Show this help message and exit
  --project PROJECT     The name of the project
  -P, --repo REPO       The repo to initialize. Can be a local path or a Git repo URL. Defaults to the current working directory.
  -t, --token OAUTH_TOKEN
                        An authentication token to access a private Git repo
  --git-identity SSH_PRIVATE_KEY
                        The private SSH key path to access a private Git repo

The command for some reason doesn't show --ssh-identity and --remove but respects and supports them. I wonder they aren't in the help message.