Use external override of default_options for Conan recipes

To minimize edits to vendored Conan recipes, we need a mechanism to override default_options specified in those recipes.

Ideally this could be done in a Conan profile, and we should be building those from versions.yaml as a source of truth.

Start by reading versions.yaml and the vendored Conan recipes to understand how default_options are currently defined and how profiles are generated. Done means an external mechanism can override recipe defaults through a Conan profile while versions.yaml remains the source of truth and vendored recipes need minimal edits.

Written by the indexing model from the issue text.