FLAG_FULLSCREEN deprecation in API 30

[!IMPORTANT] This issue is to be included in a research study, and should not be worked on

• FLAG_FULLSCREEN
  • Use WindowInsetsController.hide(int) with WindowInsets.Type.statusBars() instead.
  • Only the usage in AnkiActivity needs to be fixed. The usage in Reviewer.kt doesn't need to be fixed because the screen is deprecated

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The deprecations below don't need to be fixed because the screen that uses it is deprecated and will be eventually removed.

• View.setOnSystemUiVisibilityChangeListener
  • Use WindowInsets.isVisible(int) to find out about system bar visibilities by setting a View.OnApplyWindowInsetsListener on this view
• View.getSystemUiVisibility()
  • SystemUiVisibility flags are deprecated. Use WindowInsetsController instead.