Followup to #13735, this sets a load order for theme (and theme component) stylesheets. As per the original PR, the load order is the following
- remote theme components (ordered alphabetically)
- remote main theme (if applicable)
- local theme components (ordered alphabetically)
- local main theme (if applicable)
Theoretically, this can cause unexpected style changes on sites with many themes and components but we have tested this internally with 100+ instances and did not run into any issues.