Suspend set selected clock function

1. Make the function suspend to void UI blocking.
2. Only set the clock after a short delay to avoid users scrolling
   frquently and too many heavy calls of setting clocks.

Test: Manually tested the clock carousel is smooth
Bug: 278850684
Change-Id: Ie3c1e6f274597f97d44cea59eb533aaf9c8cc949
8 files changed