Refactor Process status components

From https://gitlab.com/arkindex/frontend/-/issues/272#note_511971764:

This could even be split further (and attached to this issue)

• TaskDetails.vue is renamed to Task.vue and handles task display and polling
• TaskPanel.vue is renamed Run.vue and displays both the task panel on the left and the graph on the right, and uses Task for each task
• RunsList.vue is renamed Workflow.vue, displays the run tabs, handles changing the routes, workflow polling and using Run to show the current run
• Main.vue should only display the basic info at the top of the page (corpus, revision, mode, state, …) and uses Workflow to show the process' workflow
• Add a index.js just for convenience, so that we can do import Status from '~/vue/Process/Status' and it imports Main