Namespace dropdown in UI doesn't work for high numbers of namespaces

#### Feature Description

We have a large number of namespaces (final count will be about 75) and the UI is not very useful for this scenario.

Ideally clicking the namespace dropdown should default into a text box to filter/search the namespaces.

Current (1.9.x) interface (there are 3 pages of this dropdown):

I recognize that I'm running a slightly older version but I also confirmed on the new version that the same problem is present. It's better in that the namespaces are now off to the side in the sidebar, but for anybody whose environments aren't at the top of the list it will mean a lot of scrolling during regular use.

Here's that same list of environments in our internal deployer tool, you can see how the experience is a lot smoother. The nice thing is that even if your use case doesn't have you using a ton of namespaces, you still get the original list to scroll through as you always have.