Handle Jira service exceptions a little better in Jira Issue Controller

What does this MR do?

Addresses followup issue #227293 (closed)

Projects::Integrations::Jira::IntegrationError will typically be an informational message, like Jira service not configured. so allow that to pass through to the user.

Projects::Integrations::Jira::RequestError is a detailed error message from the Jira service, so log it and return a more generic message, An error occurred while requesting data from the Jira service. This is to be defensive about potentially exposing any information that might be considered a security leak.

Screenshots

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