Refactor ToggleSliderView

ToggleSliderView logic is refactored into a separate controller. A
factory that creates the controller inflates the correct view so the
behavior is transparent to consumers.

The new prototype for brightness slider is here.

Allows to switch between regular brightness slider and thick one:

`adb shell settings put secure sysui_thick_brightness X`

where X is one of:
0 - regular brightness slider
1 - thick brightness slider with mirror
2 - thick brightness slider without mirror

After changing restart device or sysui:
`adb shell am crash com.android.systemui`

Test: manual
Test: atest SystemUITest
Change-Id: Ica7b31d6880c3be831d3f99115945b330ba3d618