Added material styling for SeekBarPreference in v14

Material styling was missing in v14 preferences for SeekBarPreference.
This made the PreferenceThemeOverlay.v14.Material theme to fall back
into using v7 preference layout which had incorrect text sizes w.r.t
the material text appearance.
Created a separate material layout under v14 and added the relevant
seekBarPreference styling attributes.

Bug: 34185407
Test: Inspecting the SeekBarPreference UI in SupportLeanbackDemos
after setting preferenceTheme attr for Settings theme to
@style/PreferenceThemeOverlay.v14.Material.

Change-Id: Ic3c808458614e9404b3fb37ecc01833a8a90eac8
3 files changed