Add dropdown with work item types to create task component

What does this MR do and why?

In this MR, we add the dropdown to select a work item type when creating the work item. So far, we are not using this type in the local mutation but it will be required to integrate the "real" mutation after !78414 (merged) is merged.

It also includes some little fixes like SVG paths and checking if the component exists before doing querySelectorAll

Screenshots or screen recordings

Dropdown

How to set up and validate locally

1. Enable the work items feature flag

   Feature.enable(:work_items)

2. Visit any issue
3. Add some checkboxes to issue description
4. Click on the three dots icon next to checkbox and click on Convert button
5. You should see a modal with the dropdown listing all the available work item types

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.