Fix ClassCastException when users starts A11y vision settings from out of setup flow

Root cause: Launch A11y vision settings from out of setup flow would not apply setup wizard theme (SettingsPreferenceTheme_SetupWizard). This throws ClassCastException when converting the layout to support auto-switching two-panel pattern.
Solution: Only converting the layout if launched in setup flow.

Bug: 269267419
Test: Manual testing by `adb shell am start -n com.android.settings/com.android.settings.accessibility.AccessibilitySettingsForSetupWizardActivity` for out of setup flow cases & 'adb shell am start -a android.intent.action.MAIN -n com.google.android.setupwizard/.SetupWizardTestActivity' for setup flow.

Change-Id: I16871b2fa800dd1de539b7b4b96c32ce7b2cd5c9