[Blinking Text Cursor Setting] Add developer setting under Display

* Add a custom TextCursorBlinkRateSliderPreference.
* Add TextCursorBlinkRatePreferenceController to development settings.
* Add strings for preference.
* Add tests for controller and preference.
* Add settings/accessibility OWNERS to
  TextCursorBlinkRatePreferenceController file.

Bug: 402134144
Bug: 385781377
Bug: 416557613
Flag: android.view.accessibility.text_cursor_blink_interval
Test: Manual local testing, TextCursorBlinkRatePreferenceControllerTest,
TextCursorBlinkRateSliderPreferenceTest

Change-Id: I603ad764c173cdf82e6295a83912a75e636f89ef