Add CTS tests for BrailleDisplayController APIs. Uses a standard file for the hidraw device node instead of a real character device file. This simplifies automated testing without requiring an actual connected Braille display. Bug: 303522222 Bug: 316035785 Test: atest BrailleDisplayControllerTest Change-Id: Id195100007b56e015e51f7b7b2afa46d5a5695fa