Renaming brightness slider UI logged events.

The events that log when the slider starts and stops tracking touch are
renamed to reflect the brightness-specific use case.

Test: atest SystemUITests:BrightnessSliderControllerTest
Flag: NONE
Bug: 295932558
Change-Id: I7eb5c21c546efedc6d0ea2819a0cb45e20d2fec2
3 files changed