Migrate issue trackers data

What does this MR do?

It takes data of issue trackers from services.properties and moves them to data field tables (issue_tracker_data, jira_tracker_data). It moves title and description to the respective fields on services table.

It keeps the properties data as a safeguard for case something goes wrong. I suggest we create another migration for completely cleaning the data.

Gitlab.com stats

Data from chatops, 15th January

• we have about 2.8 millions issue_tracker records
• but we have less than 27 000 issue tracker records that actually need to be handled ( select count(*) from services where category='issue_tracker' AND properties IS NOT NULL AND properties != '{}' )

Running time

• the execution is quite fast, took less than 1 second for a batch of 1000 records and about 3 seconds for a batch of 5000
• I think we can safely schedule batches of 5000 with 3 minutes delay

27_000/5000
=> 5 # batches

5 * 3.minutes
=> 15 minutes

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

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Issue: #29403 (closed)