Split Page Layout Content has set styles and no way to override them

[milemons]

Description

PageLayout.Content has marginX hardcoded here which cannot be overridden through sx props as it is nested below the box where sx props are applied. In addition, we have no way to pass an id or data- attribute down to this component to override. This causes issues for us on the new redesigned repository overview page as you can see in this discussion

Steps to reproduce

1. View issue on repository overview page ie (github.com/github/github) with the react_repos_overview flag turned on.

Version

v35.24

Browser

Chrome, Safari, Firefox, Edge