Relates to #977

The related issue introduces a coder_task data source.
Provisionerd needs to insert the following information into this data source if the workspace related to the current workspace build is related to a Task:

• Task ID (CODER_TASK_ID)
• Task prompt (CODER_TASK_PROMPT)

If this relation is not present, the associated fields should be blank.

During template import jobs, we may need to set placeholder values for these fields.