feat(A11yFeedback): Add feedback entry for Accessibility page

This entry point allows users to access in the action bar.
Visibility is controlled by the aconfig and FeedbackManager#isAvailable

Bug: 393981463
Test: atest AccessibilitySettingsTest
Flag: com.android.server.accessibility.enable_low_vision_generic_feedback
Change-Id: I8c219b8220b5839121d14959fe526e6200afeecb