Dumps magnification information when calling dumpsys accessibility

To make the magnification debugging easier, we add the dump information for magnification.

AccessibilityManagerService dumps magnification information
of the controlling magnifiers on the displays
When
1. $adb shell dumpsys accessibility
2. CTS a11y test cause failed,

Bug: 214835232
Test: manual - Turn on the magnifier and $adb shell dumpsys accessibility
Change-Id: I39c393e6c41928f303c2aee8c0d7f0f6478162f9