Remove z-index values

[danrot]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets	---
Related issues/PRs	#5035
License	MIT
Documentation PR	---

What's in this PR?

This PR removes all z-index values, and sometimes has to reorder some HTML components to make this possible.

Why?

This PR fixes a problem that occured in #5035. The dropdown filter introduced there could only be closed if something outside of the FieldFilterItem (containing the ArrowMenu) was clicked. Now it is possible to also click on the ArrowMenu to close it.

To Do

• Test in different browser

[danrot]

This does not seem to work anymore after changing the Header

[danrot]

@nnatter Tested this already in chrome, firefox and safari, and didn't encounter any errors 🙂 The important thing to test is the dropdown error you have found in #5035, this should work now as well.

[niklasnatter]

Did encounter two quirks while testing this, otherwise it is looking good:

• The DropzoneOverlay (at least i think that is what it is called) that appears when drag-and-dropping an image flickers like crazy. I think this needs to be fixed.
• Looks like the ckeditor uses z-index for parts of its interface. At least some parts cover the area of a dialog in my case. This should be fixable by setting the z-index of a container element as done for the location field type: https://github.com/sulu/sulu/blob/master/src/Sulu/Bundle/LocationBundle/Resources/js/containers/Location/location.scss#L61
  

[danrot]

@nnatter Both issues should be fixed now. And "is using z-index" becomes a new criteria when choosing a 3rd party package 🙈

[niklasnatter]

works like a charm 🙂