feat: add new trigger-renovatebot job

Add a new CI job to the common pipeline which triggers a run of renovatebot for the CI pipeline's project if the TRIGGER_RENOVATEBOT_ENABLED variable is set.

Since no jobs are added unless that variable is set, this ensures that renovatebot runs are always explicitly triggered.

The auto-devops/trigger-renovatebot.yml template also includes a template CI job which can be used to construct trigger jobs with more elaborate rulesets.

• An example pipeline run using the common pipeline from this MR which shows no job is added by default.
• An example pipeline run where TRIGGER_RENOVATEBOT_ENABLED was set showing a job being created. The job logs show a successful trigger.
• An example pipeline run where a renovatebot run was triggered for a downstream project.