Bug fixes:
- #6858 Application is blurry and unfocused on macOS
- #6872 Check for dns_sd.h only when building GUI
- #6874 The logo on Windows taskbar is incorrect.
- #6879 Update macOS installer drive icons
- #6878 Update googletest library to latest version
- #6882 Build macOS using qt 5.15.2 and avoid using brew for build
- #6884 Fix logo for Linux and dark logo for macOS
- #6886 Update Welcome screen
Enhancements: