Fix the position of a11y floating menu was not centered when switching the...

Fix the position of a11y floating menu was not centered when switching the size under half oval type.

Solution:
Adjust the compute related to the center point of the menu.

Extra action:
Fine-tune layout parameters by new resource value to meet UX style.

Bug: 189448323
Test: atest AccessibilityFloatingMenuViewTest AccessibilityTargetAdapterTest
Change-Id: I096931ed7d232877805ebca372ad370a58028abc