Make log size for job traces configurable

What does this MR do?

Allow the administrator to configure the maximum size of a job log to show in the UI. Currently it's hardcoded at 500kb but I have jobs that exceed this only slightly and cause my folding/collapsing rules to stop working as it can no longer see the entire log file with the section start end and.

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have included a changelog entry.
  • I have not included a changelog entry because _____.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

Depending on the number the end-user admin enters this can cause more date to be transfered between GitLab server and client. Also parsing the log file might take more time on the clients browser.

• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Related to #295654