Increase Jira Net timeout when fetching issues

What does this MR do and why?

For some large Jira instances, importing issues would timeout if the instance has too many issues. We have increased the network timeout for this particular request.

Change still behind the increase_jira_import_issues_timeout feature flag, now enabled by default as discussed in #356814 (comment 1637999368)

FF removal scheduled for the next release

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #356814 (closed)