Adds WindowMagnification for Accessibility in TV System UI

This adds WindowMagnification in TV SystemUI service componenets.
And with this CL, AccessibilityMagnificationTest has been passed on TV platform.
https://android-build.googleplex.com/builds/tests/view?invocationId=I62600010004928936&testResultId=TR89627840930626135

Bug: 212387167
Bug: 210052246
Test: atest CtsAccessibilityServiceTestCases
Change-Id: Iac677725348df0e78361668714e9e011a56ed5ad