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.

auto-devops/common-pipeline.yml

@@ -18,6 +18,7 @@ include:
   - local: "/auto-devops/python-publish.yml"
   - local: "/auto-devops/python-check-tags-match-version.yml"
   - local: "/auto-devops/mkdocs-docs.gitlab-ci.yml"
+  - local: "/auto-devops/trigger-renovatebot.gitlab-ci.yml"
 
   # Fail-safe workflow rules. These can be overridden by CI configuration which includes us.
   - template: Workflows/Branch-Pipelines.gitlab-ci.yml