Add controls to enable viewing Jira issues within GitLab

What does this MR do?

Issue #223787 (closed). This MR is a part of a bigger epic to allow users to integrate Jira issues and view them in GitLab.

• These specific changes add the frontend for setting up the integration and is behind the jira_integration feature flag.
  • Add a checkbox to enable Jira issues UI.
  • Add an input to specify which Jira project it should apply to.
  • Add a link to project settings to allow users to "disable GitLab issues".
• Make sure everything is integrated with the backend (saves properly) and has specs.

Screenshots

Before	Checkbox is not selected	Checkbox is selected

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team