Intent handler for new BACKGROUND_RESTRICTIONS_SETTINGS

Use the existing battery usage screen as entry point
for ACTION_BACKGROUND_RESTRICTIONS_SETTINGS.

Bug: 320150834
Test: am start -a android.settings.BACKGROUND_RESTRICTIONS_SETTINGS
      atest ActivityManagerTest#testBackgroundRestrictionsIntent
Change-Id: I479ab666334eeb3232a9200b70a6d3ce2ddd2ad9