Swap "Merge Request" and "Branches" tabs in branch view in WebIDE

Summary

When viewing a branch in Web IDE, especially one, connected to a merge request, we show dropdown above branch files in the left panel in the format:

branch-name | merge-request-id

Though when one clicks this dropdown to get a lit of all branches or all merge requests on this project, the order of the tabs in the dropdown is reversed:

merge-requests-list | branches-list

that is a bit confusing

Possible fixes

I this we should swap panels in the dropdown to follow the branch -> merge request pattern