Use title and description fields for issue trackers

What does this MR do?

• it adds description field to Service model
• it adds support to read from title and description fields but still keeps the possibility to read data from properties. Data migration will be a follow-up MR (issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/63083)
• when a new record is created, title and description are written only to the separated fields
• when a record is updated, title & description are moved from properties to their own fields

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• [-] Separation of EE specific content

Performance and testing

If cross-browser testing is not required, please remove the relevant item, or mark it as not needed: [-] -->

• 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

Closes #63690 (closed)