Track Jira import progress in a separate data structure

What does this MR do?

This MR changes quite a few files but in essence what this MR does is it replaces a PORO model JiraImportData built on top of ProjectImportData#data JSON with an AR model JiraImportState.

Because JiraImportData was initially used to track jira imports with some of the import details, it touches on quite a few parts of the application, but the changes are limited in essence to replacing the object usage, no application functionality or behavior changes are intended.

Note that Jira import is not yet released and is behind feature flag.

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

Closes #211660 (closed)