Create a template in azure-sdk-pr to support onboarding services.

- [x] Create a GitHub issue template in azure-sdk-pr repo to support submitting onboarding questionnaire. Following are the required details to collect.

1. Product Id in service tree
2. Product name
3. Product Type (Offering, Feature or Sku)
4. ProductLifecycle( Private Preview, Public Preview, GA, In Dev)
5. Service ID in service tree
6. Service name
7. Do you need to generate and release Azure SDK for your product? Below two are applicable only if this is yes. Yes or No
8. Is data plane applicable for the product (Do you need to release data plane SDK)? Yes, No, N/A
9. Is Management plane applicable for the product? Yes, No, N/A
10. Name of submitter:

- [x] Create an Azure DevOps pipeline that runs on a schedule. This Pipeline should check for new onboarding issues submitted, process the content and create a new triage work item or update an existing triage work item.
Sample triage work item: https://dev.azure.com/azure-sdk/Release/_workitems/edit/17853

- [ ] Update the documentation in the enghub to use GitHub issue for onboarding.
- [ ] Disable onboarding option in the release planner.

FYI... @MrJustinB