Fix z-index in Quick Actions dropdown

[alejandraarri]

We have a little issue with z-indexes. When you have a Quick Actions dropdown open and scroll the page, you can see the dropdown above the header. This is also noticeable with the sticky headers in the tables. So we’ve done a little refactor to improve the z-index management.

Acceptance

• Go the Home page, open a Quick Actions dropdown in Maps list and scroll the page. Check that it positions under the header of the Maps list but above the Datasets list header.
• Repeat the test in the Search results page
• Check that all dropdowns (Filters, Search suggestions, User…) are correctly positioned.

[csubira]

Nice renaming and good approach about the two stacking contents! :)

[csubira]

Acceptance done following the steps described above -> 🆗