tw29821365 - adds background option to drush command WIP

[banoodle]

Description

Teamwork Ticket(s): https://kanopi.teamwork.com/app/tasks/29821365 (for Humane World)

I wrote a cypress test that checks for certain search results, and if it finds none, it clears and reindexes search on the multidev. It essentially works, but because it takes so long to reindex, the test is almost always "failed" even though I can see things are working as I intended.

I asked AI to help me with running the reindex drush command in the background. It advised changing the shrubs drush command as I have done in this PR.

I have tested this in docksal and it works as intended.

I am in the process of testing it on the multidev by pointing composer to this branch.

Acceptance Criteria

• A list describing how the feature should behave
• e.g. Clicking outside a modal will close it
• e.g. Clicking on a new accordion tab will not close open tabs

Assumptions

• A list of things the code reviewer or project manager should know
• e.g. There is a known Javascript error in the console.log
• e.g. On any multidev, the popup plugin breaks.

Steps to Validate

1. A list of steps to validate
2. Include direct links to test sites (specific nodes, admin screens, etc)
3. Be explicit

Affected URL

link_to_relevant_multidev_or_test_site

Deploy Notes

Notes regarding deployment of the contained body of work. These should note any
new dependencies, new scripts, etc. This should also include work that needs to be
accomplished post-launch like enabling a plugin.