Resolve "Move sub_nav content above the content-wrapper class"

This MR moves the sub_nav content above the sidebar so that the sub_nav can be full-width without resorting to hacks. This is necessary prerequisite for !10096 (merged)

Closes #29880 (closed)

added 2 commits

• eb56b700 - genericise sidebar vertical offset css as it relates to the subnav
• d8d53853 - adjust the affix breakpoint to match css top value

Compare with previous version

added 1 commit

• ba686434 - update sub-nav selector in user_requests_access_spec

Compare with previous version

assigned to @annabeldunstone

@annabeldunstone can you review/merge this?

@mikegreiling this is awesome! Glad to see this stuff cleaned up.

approved this merge request

merged

mentioned in commit 35f81364

mentioned in merge request !10096 (merged)