[REQ] OpenAPI Normalizer to remove elements

Is your feature request related to a problem? Please describe.

I want to use a subset of an OpenApi document. For example a subset could be used only internally, only by administrators...
In the subset, all the unused schemas, parameters... should be removed (remove-unused-components functionality)

#22115 is an example

Describe the solution you'd like

I want to be able to selectively remove elements from an OpenAPI documents.

In conjunction with the filter normalizer, a new normalizer deletes operations, schemas, parameters...

Elements not referenced anymore can be be removed as well.

Describe alternatives you've considered

Some removal can be done with these normalizers:

• REMOVE_X_INTERNAL
• KEEP_ONLY_FIRST_TAG_IN_OPERATION

Using x-internal: true. This works in the generation phase.

Using .openapi-generator-ignore files

Using implicitHeaders option

Use redocly as suggested in #22115

Additional context

Review the existing REMOVE_X_INTERNAL and KEEP_ONLY_FIRST_TAG_IN_OPERATION normalizers, the filter normalizer, and example #22115. Define the selectable removals and unused-component behavior, then verify the normalizer against representative OpenAPI documents.