[BUG] The `--config` / `-c` parameter doesn't work when generating API client

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
  Here is a reproduction repo which demonstrates how to reproduce this issue: https://github.com/borasemiz/OpenapiGeneratorCLI-ConfigFile-Issue
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
  It should use the provided configuration file and shouldn't ask for a generator name.
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

The --config / -c parameter is either ignored or it doesn't work when generating API client. Please see the minimal reproduction repo for more details.

openapi-generator version

Version 5.1.0 and 6.0.0

OpenAPI declaration file content or URL

Please see the reproduction repo above.

Generation Details

Please see the reproduction repo above.

Steps to reproduce

Please see the reproduction repo above.

Related issues/PRs

No related issues I was able to find.

Suggest a fix

If I am using this --config parameter out of its intended purpose, please put a better description in documentation.

Start with the linked reproduction repository and the OpenAPI Generator CLI entry point handling --config/-c, comparing behavior in versions 5.1.0 and 6.0. Reproduce the prompt for a generator name and trace why the configuration file is ignored; done means API client generation uses the supplied configuration without asking for a generator name.