z-index for backdrop is not working as expected

[atifzaidi92]

Description

if we opened a side sheet or modal or dropdown list and use backdrop, backdrop z-index is less than all three components z-index

Steps to reproduce

Clear steps describing how to reproduce the issue.
use a dropdown
open the dropdown popover(option list)
add backdrop after opening the option list

Expected result

latest backdrop z-index should be maximum based on rendering order

Actual result

dropdown z-index is less than all three components

[youngheart12]

@atifzaidi92 Can you please attach a screenshot or a video for the same to better understand the problem.