Update documentation for CI/CD to include composite workflows

[potiuk]

The documentation in https://github.com/apache/airflow/blob/main/dev/breeze/doc/ci/05_workflows.md is slightly outdated. While it explains general approach properly, it does not explain the "composite workflow" grouping introduced in the last few months - i.e. all worklfows that are used with uses: ./.github/workflows/... in https://github.com/apache/airflow/blob/main/.github/workflows/ci.yml

The documentation could be updated to a bit higher level - describing the "composite" groups of workflows rather than individual jobs.

[potiuk]

This will be far simpler when we complete #43268

[KoviAnusha]

@potiuk, can I take up this one?

[potiuk]

Sure. If you manage to do all those issues :)