Testing for Fluent Theme

[singhashish-wpf]

• Each change should also have the necessary unit tests which will be run on the CI.
• Tests should cover all states of the controls. (Active, Hover, Selected etc)
• Test that the theme changes are happening correctly over different scenarios of system theme change and user theme change.
• Test that the themes are being loaded properly.
• Test that switching theme is not leading to inconsistencies.
• Test that the performance isn't getting degraded due to theme changes.
• Test 3rd party controls for proper working after theme changes
• Test all local wpf tests including DRTs, Microsuites and Feature Tests