Store worker hostname and process id when jobs are picked up for execution by workers

[rtibbles]

Requirements:

• Add a nullable field to the jobs table (to allow for alternate task runner implementations that do not add this information, e.g. the WorkManager API in the Android app context) to store the hostname and process id of the worker process that picked up a task for execution.
• Make the worker implementation annotate this data if available onto the job object when it picks up the job for execution.

Follow up from #9641