Browser-laptop: Unique icons needed for the different product channels

[bsclifton]

This is a continuation of https://github.com/brave/browser-laptop/issues/4120

We have all the icons for the product itself. However, we are missing icons for:

• installer (the EXE on Windows or the DMG once mounted)
  
  
  
  • brave_installer.icns, brave_installer.ico, brave_installer.png
  
  
• the Brave logo when inside the DMG installer
  
  
  
  • background.png
  
  
• the Brave logo when inside the Windows installer
  
  
  
  • brave_splash_installing.gif
  
  

cc: @darkdh

The work to create separate channels was done with https://github.com/brave/browser-laptop/pull/10552

[bradleyrichter]

@bsclifton Here are the new app icons for all build types:

Brave_Desktop_iconset.zip

[bsclifton]

@darkdh should be an easy one if you wanted to grab this 😄 👍

[bradleyrichter]

@darkdh ok, refreshed ZIP and previews above...