Remove grid scaling in Overveiw

- Grid scaling has problem that scales task icon and menu, which makes it hard to control icon size and text size in the manula
- Replaced the whole concept with dedicated Task size calculation in grid layout
- Support different icon size in TaskView in grid and removed task_thumbnail_top_margin
- Removed grid progress in TaskViewSimulator as well
- Refactored how ClearAllButton scroll and translations are calcualted to align clear all properly in grid
- Make page center calculation aware of PagedView pivot and scaling

Bug: 174464863
Test: Manual on two screens
Change-Id: I47b13ef6e55c6e16c52ea04225f5bde02ed82fc2