Default templates inside project for issues and MRs in Free

Proposal

Be able to assign a MR template by default to all MR instead of selecting it every time.

Links / references

https://forum.gitlab.com/t/set-mr-template-as-default/3995

Documentation to update

If this feature is moved, we'll need to update this documentation page and other mentions in the docs and on about.gitlab.com.

Docs style guide on documenting moving a feature to another tier: https://docs.gitlab.com/ee/development/documentation/styleguide/index.html#version-text-in-the-version-history

Current Status

After reviewing this proposal and the supporting evidence in this confidential issue (https://gitlab.com/gitlab-com/Product/-/issues/2631), there was unanimous approval for moving default description templates to Free.

Implementation Tasks

• Move related code from EE to CE for default Issue Templates
• Move related code from EE to CE for default MR Templates
• Documentation update