Migrate SendStatusService from ForegroundService to data transfer job

[nikclayton]

Per https://developer.android.com/about/versions/14/changes/user-initiated-data-transfers, SendStatusService, currently implemented as a ForegroundService, could be migrated to starting data transfer jobs instead.

This might give simpler code; e.g., there would be one job per outgoing post, instead of SendStatusService needing to maintain a queue (statusesToSend) of outgoing posts