adservices: optionally start AdServicesManagerService on Wear

Use flag and system property to customize the whether starting the
AdServicesManagerService.

Flag: android.server.remove_ad_services_manager_service_from_wear
Test: build & presubmit
Bug: 340928611
Change-Id: I1a7c4213c96b43d56cd83bd580c0fe744362c577