Add schedule setting page for time-based modes.

Creates new layout for setting the start & end time, and days of the week, for a schedule-based mode.

This is close to the mocks specified in https://screenshot.googleplex.com/8zmb7PAjjt73VkN, but with the following differences:
- the end time is left-aligned with the center rather than on the right side of the screen. This is a side effect of using LinearLayout to evenly space start & end times, and could in theory be fixed by using a ConstraintLayout, but that option seems to cause times to overlap instead of wrap when display size is cranked up. Could be fixed later.
- no icons yet on either side of the time display
- no Done button. Instead, has the "exit at alarm" switch that exists today.

Have not yet checked how this interacts with TalkBack, etc.

Flag: android.app.modes_ui
Bug: 332730302
Test: ZenModeSetSchedulePreferenceControllerTest, ZenModeExitAtAlarmPreferenceControllerTest, ZenModeSetTriggerLinkPreferenceControllerTest
Test: manual: interacting with UI in normal size, with font & display at minimum and maximum, and in locales (fr) where the first day of the week is a different day
Change-Id: I0b76f55891d6c12fc27720657c9eea6fe42fbafe