Use work item type in UI text

What does this MR do and why?

Fixes #368003 (closed) - use work item type when creating, updating, or deleting a work item.

Update the following UI text:

before	after
Task deleted	%{workItemType} deleted
Are you sure you want to delete the task? This action cannot be reversed.	Are you sure you want to delete the %{workItemType}? This action cannot be reversed.
Delete task	Delete %{workItemType}
Something went wrong when creating a task. Please try again	Something went wrong when creating %{workItemType}. Please try again.
Something went wrong when deleting the work item. Please try again.	Something went wrong when deleting the %{workItemType}. Please try again.
Something went wrong while updating the work item. Please try again.	Something went wrong while updating the %{workItemType}. Please try again."

Moves most UI text to constants.js, and pass in the workItemType string. This means components can import i18nForType instead of needing to import s__, sprintf, and capitalizeFirstLetter.

How to set up and validate locally

1. Enable work_items and work_items_mvc_2 feature flags
2. Go to gdk.test:3000/gitlab-org/gitlab-test/-/work_items/new to create a new work item
3. To force errors in creating/updating. Either gdk stop (after loading the page), or Disable network in throttling section of Network tab in devtools
4. To view delete, create a work item, click ellipsis menu