[UX] Show all supported arguments with `--help` for `dstack apply` regardless of the configuration type

[peterschmidt85]

Currently, the user has to type dstack apply --help task.

[github-actions]

This issue is stale because it has been open for 30 days with no activity.

[github-actions]

This issue was closed because it has been inactive for 14 days since being marked as stale. Please reopen the issue if it is still relevant.

[r4victor]

#2269 added a hint to use -h type if only -h is specified:

dstack apply -h
Usage: dstack apply [--project NAME] [-h [TYPE]] [-f FILE] [-y] [--force] [-d]
                    [-P REPO] [--repo-branch REPO_BRANCH] [--repo-hash REPO_HASH]
                    [--no-repo] [-t OAUTH_TOKEN] [--git-identity SSH_PRIVATE_KEY]
                    [--ssh-identity SSH_PRIVATE_KEY] [--local]

Options:
  --project NAME        The name of the project. Defaults to $DSTACK_PROJECT
  -h, --help [TYPE]     Show this help message and exit.
  -f, --file FILE       The path to the configuration file. Defaults to
                        $PWD/.dstack.yml
  -y, --yes             Do not ask for confirmation
  --force               Force apply when no changes detected
  -d, --detach          Exit immediately after sumbitting configuration

Repo Options:
  -P, --repo REPO       The repo to use for the run. Can be a local path or a Git
                        repo URL.
  --repo-branch REPO_BRANCH
                        The repo branch to use for the run
  --repo-hash REPO_HASH
                        The hash of the repo commit to use for the run
  --no-repo             Do not use any repo for the run
  -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
  --ssh-identity SSH_PRIVATE_KEY
                        The private SSH key path for SSH tunneling
  --local               Do not use Git

Type `dstack apply -h CONFIGURATION_TYPE` to see configuration-specific options.

Merging all the arguments across configurations using built-in argparse is not possible since different configuration have conflicting options. Even with a custom output, showing all the arguments would be too verbose and clumsy.

@peterschmidt85 I think showing the hint is sufficient and I'd close the issue.