Adds 'App info' button on accessibility service + activity pages.

This launches the existing app info page for the a11y feature's owning
package. Features without a valid component (framework features) do not
have this button. This is also not shown in Setup Wizard which does
not support the App Info page.

This helps users find more info about the app that provided an
accessibility feature.

Screenshot: https://screenshot.googleplex.com/B9FXLoomxFjLBv8.png
Flag: accessibility com.android.settings.flags.accessibility_show_app_info_button

Bug: 277378550
Test: atest ToggleFeaturePreferenceFragmentTest (robotest)
Test: Open and interact with the button, ensure it opens the app info
      page for the correct app.
Change-Id: I2041c09077ce5fadc72117dc0c72409dd33ef60b