Add controls to enable viewing Jira issues within GitLab

Problem to solve

Controls need to be added to the existing Jira integration to allow the user to enable the viewing of Jira issues within GitLab.

Because the integration is today is not limited to a specific project, and works instance wide (i.e. you can mention any Jira issue from the project within an MR or commit and it will add a comment), We need a way to:

1. Scope this specific feature to a Jira project(s)
2. Enable the viewing of Jira issues
3. Enable/disable GitLab issues

Proposal

Add a new section to the bottom of the existing Jira integration called: View Jira issues in GitLab

See Designs tab for mockup.

Todo

• Get engineering feedback & iterate on flow if needed
• Add Technical Writing label and improve micro copy