Increase touch region for checkbox in letterbox restart dialog

Make the touch region to toggle the checkbox state a minimum of 48x48dp
around the checkbox itself as well as the text and parent container
associated with the checkbox. Thus making the new touch region 48dp high
and the width of the parent container

Fixes: 278589504
Test: atest WMShellUnitTests:LetterboxEduDialogLayoutTest
Test: atest WMShellUnitTests:LetterboxEduWindowManagerTest
Test: atest WMShellUnitTests:CompatUIControllerTest
Change-Id: Ia124897f92717eea4ddef3b2431a43adedde0f8c