Follow up - Add new sidebar location for Exploring GitLab

Description

This is a follow up issue to the following

Additional improvements (may warrant splitting out)

• Project page – with the removal of 2 of the tabs on this page, we can eliminate the current nesting for the "Yours" Tab ("All" & "Personal") and include those as Tabs at the top level . → #415095 (closed)
• Projects & Groups pages – For better layout consistency (matching pages like Issues, MRs, To-Dos), as well as to handle responsive better, move the Filter and Sort options to be within their own row/section directly above the results (underneath Tabs when present). → #415098
• Remove the unnecessary line break (border) directly under the Page Title on the pages in "Your work" (and make sure to not include this line break on "Explore" pages) - Handled in !114017 (merged)
• Issues page – Update the "Subscribe to RSS feed" and "Subscribe to calendar" buttons to be icon-only buttons with a tooltip (similar to how we handle this on the Issues page within Groups/Projects. → Resolved with !114157 (merged)