Revert "Remove selection toolbar code from build time"

Relevant things that were never originally removed:
  DefaultSelectionToolbarRenderService declaration in
      core/resAndroidManifest.xml
  Permission definition for BIND_SELECTION_TOOLBAR_RENDER_SERVICE

Changes made:
  Use class instead of hardcoded string in SystemServer
  Use InputTransferToken to fix build error
  Updated OWNERS file
  Use Flags instead of DeviceConfig

This reverts commit cc8461dd.

Bug: 363318732
Test: TextViewIntegrationTest TextViewMouseInteractionTest and manual
Flag: android.permission.flags.system_selection_toolbar_enabled

Change-Id: I145912582882d82a0640d8ea675789b93ee8d330