Add multi-display support to FloatingToolbar.

DecorView has no support for multi-display (bug 65172902).
Until that is done, the easy fix for displaying cut, copy, paste
on non-default display is to modify FloatingToolbar.
FloatingToolbar uses context of Default display. Changed it
to use context of the window (which makes it multi-display
compatible).

Fixes: 64837794
Test: Manual using AAe's KitchenSink test app
bit FrameworksCoreTests:android.widget.TextViewActivityTest
bit CtsWidgetTestCases:android.widget.cts.TextViewTest
Change-Id: I513f1aac1c0d22355c996247e3bf56c6d812348f