[issue_tracker] Add stress testing tool

[Montekkundan]

Brief summary of changes

• Adds a sandbox-only CLI tool for generating Issue Tracker stress-test data.
• Supports generating up to 100,000 issues with configurable comment distributions and batch sizes.
• Generates varied statuses, priorities, categories, and assignees.
• Adds dry-run, tagged-run, and targeted cleanup support.
• Adds a manual test plan covering 1,000 through 100,000 issues.

Testing instructions

• Confirm dev.sandbox is enabled in the local LORIS configuration.
• Preview a run:
  php tools/issue_tracker_stress_test.php --issues=1000 --comments=0,1,5 --run-id=stress-1
• Generate the data by adding --confirm.
• Open http://localhost:8080/issue_tracker/.
• Filter the Title field by stress-1 and confirm the generated issues load.
• Open generated issues and confirm their configured comments appear.
• Test filtering, sorting, pagination, and issue-detail loading.
• Remove the generated data:
  php tools/issue_tracker_stress_test.php --cleanup=stress-1 --confirm
• Run npm run lint:php.

Link(s) to related issue(s)

• Resolves [issue_tracker] Stress Testing #10811

[skarya22]

Thanks for trying this! Can you also try performing the stress test on the frontend ui for both regular and batch edit to see if it works still ?

[regisoc]

Thanks for this PR! Nice work.
I am not able to test the test plan fully as I have some issues with my VM, but at high numbers of issues/comments, it correlates with errors we have in HBCD. I will try to have my VM in shape for a more thorough pass.
For now, my comments included below.

Minors blocks to change, the global logic makes sense:

• dry-run/confirm: pick one. It will be easier to understand and remove some checks.
• extract both main feature (insert issue and clean issues) into clear functions.
• Do we need to keep track of the attachments?

[Montekkundan]

• Reused generic_includes.php.
• Removed the redundant --dry-run option.
• Simplified generation and cleanup dispatch.
• Removed the hardcoded lorisadmin username and unnecessary attachment handling.
• Added the requested helper and validation updates.
• Expanded the frontend test plan.

Tested with 1,000 issues and 1,998 comments. Browse Issues and issue details worked correctly. Batch Edit still failed after all generated data was removed, including with the normal raisinbread issues, so that appears to be a pre-existing issue.
Ready for another review, thanks!