drop support for tool_metadata.yml

### Description

What was a convenience for OpenLane is no longer really in use by any other tool and we need so much special behavior that introduces bugs instead of simply making a required argument that is handled by click.

See #128 for what happens as an example.

### Proposal

Ciel 3.0.0 should drop support for tool_metadata.yml.

Start by reviewing issue #128, then locate the tool_metadata.yml handling and the Click entry point that currently provides its special behavior. The work is complete when Ciel 3.0.0 no longer supports tool_metadata.yml and the required argument is handled by Click without the existing compatibility path.

Written by the indexing model from the issue text.