Update popup and arrow positioning logic

1) By default, it's centered relative to the event position
   https://screenshot.googleplex.com/5Wri2CX3vASCxWt
2) It becomes left or right aligned near edges of the screen
   https://screenshot.googleplex.com/9AEQxWcmYX63jTv
   https://screenshot.googleplex.com/39KMeG2eWKr2QC6
3) And never goes beyond the minimum padding
   https://screenshot.googleplex.com/5LiPHiXiJSyGdx5
   https://screenshot.googleplex.com/86KQnKXa38NoYpM

Bug: 297325541
Flag: com.android.launcher3.show_taskbar_pinning_popup_from_anywhere
Test: manual, flip the flag, open popup from different positions
Change-Id: I06cf0c0352da946da7a62413144c304623557216