Raise support bot permission to reporter

What does this MR do?

Raises support bot permissions to reporter when service desk is enabled.

This is a follow up from #2030 (closed) and allows
quick actions to be performed by support bot when present on the issue description template, like changing milestone, assignee, adding labels etc.

We need to keep an eye if raising support bot permissions to reporter can cause any security issue.

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

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