Work Item UI Cleanup

Problem

There are a few wonky things happening with work items that we need to address.

Cleanup

• Change "Delete work item" to "Delete task" (Fixes all visible mentions of work items in UI (!92029 - merged))
• To allow work items to be closed on mobile, move the action menu three dot icon to a row above the title. When the work item is being rendered in a modal, show an X close action to the right of the three dot icon.
• Include the work item type indicator in the top... (#366221)
• Fix dark mode styling when viewing the work item within its route (title border always visible, background color on buttons) [1]
• Status dropdown doesn't look great -- overlays the input. The options should open below the field.
• Move Description's Save and Cancel buttons to the lower left of the input when in editing mode. [1]
• When a task has no parent, the breadcrumbs lose the Task icon (ex: https://gitlab.com/gitlab-org/plan-stage/test-project/-/work_items/113201444)

[2]